Fitness numbers are useful when you know what they mean. Use these formulas and charts to understand your training, plan with your coach, and follow your progress. Some answers are straightforward calculations. Others are estimates that need a little context.
By TTAE Staff · October 15, 2026
Your inputs stay in this page. No accounts, saved measurements, or health-data collection.
Calculation Arithmetic from your inputs; measurement errors still matter.
Estimate A model predicts something not directly measured.
Screening measure One part of a wider assessment, not a diagnosis.
Effort guide A subjective check, not a laboratory measurement.
General education for adults. Medication, disease, pregnancy, growth, and eating-disorder concerns need an individualized plan. These tools do not replace it. Example numbers are illustrations, not recommended targets.
Strength
01
Estimate
Estimated one-rep max
What might an already-recorded set suggest about this lift?
Formula or method
Brzycki estimated 1RM = load ÷ (1.0278 − 0.0278 × repetitions). The result uses the load unit. The common 36 × load ÷ (37 − repetitions) version is a close approximation, not identical.
Worked example. 100 lb × 8 repetitions → estimated 1RM of about 124 lb. This does not establish that you can safely lift 124 lb.
When to use it · why it helps
Compare recorded sets in the same exercise when setup, technique, and effort are reasonably consistent. It puts a working set in context; a coach can judge whether a set is suitable.
What it cannot tell you
The underlying assumption is repetitions to fatigue. A set stopped with several repetitions left does not meet it. Exercise and individual endurance affect accuracy. This tool accepts 2–10 whole repetitions as an editorial boundary, not a validity guarantee. Do not perform a maximum test or train to failure for this calculator. No guessed repetitions in reserve are added.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
02
Calculation
Percentage-based lifting loads
What load corresponds to a percentage already in your program?
Formula or method
Target load = reference maximum × percentage ÷ 100. Conversely, load ÷ reference maximum × 100 gives the percentage.
Worked example. A 200 lb reference × 70% = 140 lb.
When to use it · why it helps
Translate a coach-selected percentage into equipment weight. Identify whether the reference is measured, estimated, or a separately defined training maximum. Round only after calculating.
What it cannot tell you
This arithmetic does not choose an intensity or assign a repetition count. Estimated inputs carry uncertainty. Equipment rounding changes the actual percentage; the rounded load still needs judgment. A small study found repetitions at a given percentage varied by exercise.
Chart A · Program percentages
This converts percentages from your program. It does not choose the right load for you.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
03
Calculation
Sets, reps, and volume-load
How much external load did the recorded sets add up to?
Formula or method
Volume-load = sum of repetitions × external load for each set. Use sets × reps × load only when all sets match. Units: lb-reps or kg-reps.
Worked example. 3 × 8 × 100 lb = 2,400 lb-reps. Sets of 8, 8, and 6 at 100 lb total 2,200 lb-reps.
When to use it · why it helps
Summarize changes within the same exercise. Record working-set count alongside volume-load, whether warm-ups are excluded, and whether dumbbell load is per hand or combined.
What it cannot tell you
This is not mechanical work, calories, or a muscle-growth score. Different exercises, ranges of motion, machines, and effort levels cannot be ranked by tonnage alone. More recorded volume does not prove you need more.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
Cardio
04
Calculation
Pace, speed, distance, and time
How does your recorded time translate into pace and speed?
Formula or method
Speed = distance ÷ time. Pace = time ÷ distance. With mph, minutes/mile = 60 ÷ speed. Time = pace × distance with matching distance units. One mile = 1.609344 km exactly.
Worked example. 3 miles in 30:00 = 6 mph = 10:00/mile. A pace of 9:30 is 9.5 minutes, not 9.30.
When to use it · why it helps
Translate treadmill settings or a walk/run log. Use the same time convention when comparing sessions.
What it cannot tell you
GPS error, stops, calibration, grade, wind, and terrain affect interpretation. Pace alone does not establish effort or fitness. Zero or negative time/distance and seconds of 60 or more are invalid.
Chart B · Speed to pace
Constant speed; rounded to the nearest second. Arithmetic conversion, not an effort ranking.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
05
Calculation / estimate
Heart-rate reserve
What does a selected reserve percentage mean in beats per minute?
Formula or method
HR reserve = maximum HR − resting HR. Target = resting HR + (percentage ÷ 100 × reserve). Optional Tanaka age-predicted maximum = 208 − 0.7 × age in years.
Worked example. Maximum 180 bpm, resting 60 bpm, selected 50% → 120 bpm. Age 40 predicts a maximum near 180 bpm. These are arithmetic examples, not target recommendations.
When to use it · why it helps
Understand a target selected by a coach or clinician. Reserve percentage and maximum-HR percentage are different calculations.
What it cannot tell you
Age prediction can miss an individual maximum; it is not a ceiling or safety limit. Medications, especially beta blockers, and medical conditions can change the response. Follow individualized guidance and do not perform an unsupervised maximum-HR test. The age model concerns healthy adults; this tool limits prediction to adults 18–81 as a conservative editorial range.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
06
Effort guide
Effort and the talk test
How hard does this aerobic activity feel to you?
Formula or method
CDC general 0–10 effort convention: 0 is sitting; 10 is maximum effort. Relative moderate effort is about 5–6; vigorous effort begins around 7–8.
Worked example. Two people can walk at the same speed and report different effort. That is useful information.
When to use it · why it helps
Use a quick subjective check during ordinary aerobic activity when a wearable is unavailable or questionable.
What it cannot tell you
A label of 0–10 alone does not identify a standardized scale. Do not mix these CDC anchors with the ACSM infographic, Borg 6–20, or lifting RPE/RIR. Speaking cues do not locate one exact physiological threshold. Symptoms and prescribed clinical limits take priority.
Chart C · How hard does this feel?
5–6 / 10
Moderate relative effort
Conversation is possible; singing is difficult.
Begins at 7–8 / 10
Vigorous relative effort
Only a few words fit before a breath.
Original layout using CDC descriptions. Other effort scales use different anchors. This guide is separate from heart-rate calculations.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
Nutrition
07
Calculation
An agreed protein target in grams
How many grams correspond to a target you have already agreed on?
Formula or method
Protein grams/day = body weight in kg × selected grams/kg/day. Pounds × 0.45359237 = kilograms.
Worked example. 75 kg × an example target of 1.6 g/kg/day = 120 g/day, including food and supplements. The example is not a universal prescription.
When to use it · why it helps
Translate an individually agreed target into a practical daily total. Enter your own target; this tool does not choose one from a goal.
What it cannot tell you
ISSN discusses roughly 1.4–2.0 g/kg/day for many healthy exercising people. Morton’s 49-trial analysis estimated a group breakpoint near 1.6 with substantial uncertainty, not an individual ceiling. A short intensive energy-deficit trial comparing 1.2 and 2.4 does not establish a general recommendation. Clinical nutrition requires appropriate professional guidance. No silent substitution of goal or lean body weight.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
08
Estimate
Resting energy and daily estimates
How is an initial energy prediction calculated?
Formula or method
Mifflin–St Jeor resting kcal/day = 10 × kg + 6.25 × cm − 5 × age + coefficient. Original male equation: +5. Original female equation: −161. Optional daily illustration = resting estimate × selected activity factor.
Worked example. Original male equation, 80 kg, 180 cm, age 40 → about 1,730 kcal/day at rest. An assumed factor of 1.5 gives about 2,600 kcal/day; it is not an eating target.
When to use it · why it helps
Explain the assumptions behind an estimate before interpreting it with a qualified professional and real-world observations.
What it cannot tell you
The original model used 498 healthy adults aged 19–78. It is a prediction of resting expenditure, not a measurement of daily needs. Historical sex coefficients are not validation across every sex/gender or medical context. Activity multipliers add uncertainty. This tool gives no deficit, exact eating target, or promised rate of weight change. It does not support minors, pregnancy/breastfeeding, or medical nutrition decisions.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
Progress
09
Calculation
Percentage change
How large is the change relative to a positive starting value?
Formula or method
(New − starting value) ÷ starting value × 100. Also show new − starting value in the measurement’s own units.
Worked example. 100 → 110 lb is +10%. A fixed-distance time of 30 → 27 minutes is −10% time, while speed rises about 11.1%. “10% faster” is ambiguous.
When to use it · why it helps
Put change in perspective while retaining absolute values and dates. Use the same units and measurement method.
What it cannot tell you
A positive, nonzero baseline is required. This does not identify a cause, statistical significance, or change beyond measurement noise. A body-fat estimate of 25% → 23% is −2 percentage points and −8% relative change.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
10
Descriptive summary
One reading vs. the trend
What do repeated measurements show together?
Formula or method
Mean = sum of available values ÷ count. For a seven-day window, average only measurements actually recorded within that window; show the count and missing days.
Worked example. 180, 181, 179.5, 180.5, 179, 180, 179 lb average 179.9 lb. This is a summary, not a body-fat estimate.
When to use it · why it helps
Look beyond one reading under consistent equipment, timing, clothing, and measurement-site conditions. Pair body measurements, if desired, with a relevant performance or habit measure.
What it cannot tell you
Seven days is a display choice, not a mandatory weighing schedule. Frequent weighing is optional. Missing values are not zero. A moving average lags and cannot identify physiological causes. Do not splice different body-composition methods into a continuous trend. NHS guidance describes weekly-to-monthly weighing; one standardized trial found limited extra value in duplicate days.
Chart D · One reading vs. the trend
Fictional teaching data. Dots are daily readings; the line is a trailing mean of up to seven available readings. Early windows are shorter. Neither direction is labeled good or bad.
Coral dots: daily readings. Lime line: trailing mean. Method: arithmetic mean of up to seven fictional observations.
Accessible data table and averaging counts
Fictional pounds; no missing days in this illustration.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
11
Screening measure
BMI: what the number measures
What is body weight relative to height?
Formula or method
BMI = kilograms ÷ meters². This tool uses exact unit conversion (lb × 0.45359237; inches × 0.0254) before calculating, rather than the approximate U.S. factor 703.
Worked example. 180 lb and 70 inches → BMI about 25.8 kg/m².
When to use it · why it helps
Understand a common clinical screening number as one piece of a broader assessment.
What it cannot tell you
BMI does not distinguish fat, muscle, and bone, measure fitness, or diagnose health. Adult CDC categories apply at age 20 and older, not to children and teens. A training program cannot be judged by BMI alone. Clinical context matters.
Optional adult category context
CDC adult ranges: below 18.5; 18.5 to below 25; 25 to below 30; and 30 or above, conventionally termed underweight, healthy weight, overweight, and obesity. These are screening labels, not judgments of fitness or personal worth. The calculator deliberately reports the number without assigning a category. A rounded display at a boundary may conceal the unrounded value; consult the unrounded measurement and clinical context.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
12
Screening measure
Waist-to-height ratio
How does waist circumference compare with height?
Formula or method
Waist circumference ÷ height, in the same units. The ratio has no unit. Measure the waist midway between the lower ribs and top of the hips, after a natural exhalation.
Worked example. A 34-inch waist ÷ 68-inch height = 0.50.
When to use it · why it helps
Understand central-adiposity screening alongside other clinical information.
What it cannot tell you
Not a body-fat percentage or a measure of training ability. NICE is UK clinical guidance: its adult classifications are used with BMI below 35. The tool reports a ratio without a risk category. Do not use it in pregnancy. Risk does not jump suddenly at one hundredth, and a smaller number is not automatically better.
NICE adult interpretation context
For adults with BMI below 35, NICE identifies increased central adiposity beginning at 0.5 and higher risk at 0.6. This is UK clinical guidance, not a universal U.S. fitness standard. A ratio below 0.5 does not establish health. Use unrounded measurements at boundaries; a displayed 0.50 can lie just below or above 0.5.
Editorial review: October 15, 2026. Focused source check, not a systematic or independent clinical review. Research links marked abstract were not reviewed as full papers. Formula definitions, published guidance, study findings, and practical editorial choices are distinct.
Put progress in context
Compare like with like, interpret the conditions, and keep a useful record.
13
Calculation
Compare your progress
What changed between two comparable observations?
Record the same lift, fixed-distance walk, or measurement on two dates. Keep the unit, equipment, technique, range of motion, assistance, and timing comparable. For a lift, keep repetitions and effort comparable too. This tool describes the difference; it cannot tell you why it happened.
100 → 110 lb is +10 lb and +10%. A 30:00 → 27:00 time over the same distance is −180 seconds and −10% time; speed rises about 11.11%. Say which quantity changed.
Two readings are a starting point
Sleep, fatigue, familiarity, technique, equipment, and measurement conditions may differ. More observations under comparable conditions help you interpret a pattern. No result here establishes clinical significance or separates training effects from noise. A zero starting value permits an absolute difference, but percentage change is undefined.
Method and limits
Absolute change = second − first. Relative change = (second − first) ÷ first × 100, only for a positive first value. For a fixed distance, speed change = (first time ÷ second time − 1) × 100. Both times must be positive. These are arithmetic definitions, not thresholds for meaningful progress.
Reps in reserve (RIR) is your estimate of how many more repetitions you could have completed with the same agreed technique and range of motion. Finish 8 reps and estimate about 2 more were possible? Record about 2 RIR. This describes the set; it is not a target for every workout.
One RIR-based lifting RPE scale
RPE 7 ↔ about 3 RIR About three more reps meeting the agreed standard.
RPE 8 ↔ about 2 RIR About two more reps meeting the agreed standard.
RPE 9 ↔ about 1 RIR About one more rep meeting the agreed standard.
RPE 10 ↔ about 0 RIR No further rep meeting that standard is estimated to be available.
These lifting-set numbers are not interchangeable with cardio effort or a whole-session rating. They are not a pain or symptom scale.
An estimate, not a demand to fail
People can misjudge repetitions remaining, including experienced lifters. Record the estimate after a set alongside exercise, load, and reps. Agree what counts as a rep first. You do not need to attempt a failed rep to record RIR, and reaching failure is not required for progress. Report pain or other symptoms separately.
Different studies, different programs
An eight-week study of 18 trained adults found similar average quadriceps growth with failure and 1–2 RIR, with more immediate fatigue after failure. Another eight-week study of 42 young trained adults using single-set routines found gains in both groups, with some muscle-size measures modestly favoring failure. These results do not establish one ideal RIR for everyone or every exercise.
Refalo et al. (2024) — abstract and plain-language summary reviewed; 18 trained adults, eight weeks, within-person leg comparison. Full paper not reviewed.
Hermann et al. (2025) — abstract reviewed; 42 young trained adults, eight-week single-set program. Full paper not reviewed.
By TTAE Staff · October 15, 2026. Scale explanation and research findings are distinct from an individualized training prescription.
15
Interactive interpretation guide
Why today’s number can be different
A result reflects current performance, conditions, and how it was measured. A single change cannot tell you which changed. Choose a fictional example to explore what to record before drawing a conclusion.
The observation
You complete fewer reps after a demanding week.
A more useful next step
Note recent training, sleep, and other demands. Compare similar sessions before deciding this is a lasting change in fitness. This reading does not diagnose overtraining.
Illustrative situations, not predictions of how much your results should change. There is no universal percentage that separates measurement variation from meaningful change across every test.
Keep comparisons interpretable
Keep exercise instructions, movement standard, range of motion, warm-up, rest, equipment, and conditions similar where practical. Record differences. A hand-timed sprint and an electronically timed sprint are not directly interchangeable. More consistent observations are more useful than explaining one reading after the fact.
Much of this performance guidance comes from sport and high-performance settings. Applying the comparison principle more broadly is an editorial interpretation; athlete-specific effects and targets are not assumed for every person. Tracking context cannot diagnose a persistent symptom.
Body-weight and body-composition tracking are optional. Strength, skills, activity, and how training feels can be useful measures of progress. Choose the question before the tool: what decision would a number help you make?
Scale weight
Measures: total body mass at that moment, including water and everything else your body contains.
Repeat consistently: same scale on a firm, level surface, similar time and clothing.
Limit: cannot separate fat, muscle, and water or identify which changed.
Waist circumference
Measures: circumference at a defined abdominal site.
Repeat consistently: same landmark, level snug tape without squeezing, and the same point in a normal breath.
Limit: technique and location matter; this is not total body-fat percentage. Different protocols use different landmarks. Do not mix them.
Bioimpedance (BIA)
Estimates: body water and composition using an electrical signal and prediction equations.
Repeat consistently: same device and its preparation instructions; note unusual food, fluid, or exercise conditions.
Limit: hydration, intake, device equations, and the population used to develop them affect interpretation. Decimal places do not guarantee accuracy.
Skinfolds
Measures: skin and underlying fat thickness at selected sites. Equations may convert these into estimated body-fat percentage.
Repeat consistently: trained measurer, consistent sites, same method.
Limit: measurer, calipers, and equation matter. A measured skinfold and a calculated whole-body percentage are different things.
DXA scan
Estimates: fat, lean soft tissue, and bone mineral from low-dose X-rays, including regional information.
Repeat consistently: qualified service, preparation, positioning, and equipment. Ask what change the service can reliably detect.
Limit: food, fluid, positioning, and systems affect results. Lean soft tissue is not a direct muscle measurement. DXA body-composition scanning is contraindicated during pregnancy.
No method supplies a single fitness score
Methods measure different things and make different assumptions. BIA, skinfold, and DXA percentages are not interchangeable; do not join them into one seamless trend. A method can repeat consistently while being systematically high or low. None of these numbers diagnoses health or assigns body quality.
Terms and interpretation
Fat-free mass includes water, organs, muscle, and bone; it is not another name for muscle. DXA lean soft tissue excludes bone mineral but includes tissues and water other than skeletal muscle. Body-fat percentage estimates the share of total mass attributed to fat.
Body size, age, health context, and the method’s validation population affect interpretation. Choose a method that helps your question and feels useful to you, with a qualified professional where appropriate. A food- or fluid-related change in a report does not establish a matching change in muscle or fat tissue.
CDC/NHANES waist protocol (2021) — relevant official protocol section reviewed; uses an iliac-crest landmark. Other protocols may differ.
NSCA: three field methods — indexed public excerpt text reviewed; direct retrieval timed out. Broad numerical accuracy claims from this older source are not adopted.
Tinsley et al. (2017) — abstract reviewed; food/fluid study, 48 participants. Full paper not reviewed.
By TTAE Staff · October 15, 2026. Source checking is not an independent clinical review.
17
Printable worksheet
Your personal scorecard
Which few measures help you do what matters to you?
Choose one suitable measure in each area you want to follow. You can leave any area blank. This card records observations; it does not prescribe a maximum test or combine unlike measures into one score. Body weight is optional.
Examples to adapt: the load and repetitions of a familiar lift; time on your usual walk with the same aid and route; how an everyday task felt; or the number of planned sessions completed. Record units and conditions so the next observation is interpretable.
By TTAE Staff · October 15, 2026. Editorial planning worksheet; not a validated clinical instrument.
18
Supervised screening reference
Age references without a fitness ranking
What can one supervised lower-body assessment tell an older adult?
The CDC STEADI 30-second chair stand is an older-adult screening reference for ages 60–94. It is not a general fitness ranking, a solo speed challenge, or a test for every age. Ask a qualified assessor whether it suits your circumstances.
Suitability comes before comparison
Seek individualized advice for recent injury or surgery, painful movement, dizziness or unsteadiness, unstable medical conditions, or existing restrictions. During assessment, stop for pain, dizziness, chest discomfort, unusual breathlessness, or unsteadiness and obtain appropriate medical advice. This is not an exhaustive list of contraindications.
One exact protocol
A trained assessor confirms suitability and stands beside the client. Use a straight-backed chair without armrests, a 17-inch (43.2 cm) seat, and a stopwatch.
Sit in the middle of the seat, feet flat and back straight. Cross wrists, place hands on opposite shoulders, and hold arms against the chest.
At the start signal, stand fully and sit repeatedly for 30 seconds. The assessor counts full stands and counts the final attempt if the client is more than halfway up when time expires.
If arm assistance is needed, stop. CDC records zero under this standard protocol. This means the test required assistance; it does not mean “zero strength.”
CDC chair-stand below-average scores
Units: stands in 30 seconds. Each value is a strict boundary for a below-average score, not a mean, a percentile, or a minimum fitness goal. For men aged 60–64, 13 is below the threshold; 14 is not below it.
CDC STEADI source groups and exact inequalities, ages 60–94
Age (years)
Men: below average
Women: below average
60–64
<14
<12
65–69
<12
<11
70–74
<12
<10
75–79
<11
<10
80–84
<10
<9
85–89
<8
<8
90–94
<7
<4
Source: CDC STEADI, 30-Second Chair Stand (2017). Original material is available free from CDC. Use of this material does not imply endorsement by CDC, ATSDR, HHS or the U.S. Government.
A comparison is not your goal
A below-threshold result is a reason to discuss function and fall risk with a qualified professional. Being at or above it does not rule out fall risk or establish overall fitness. Goals should reflect daily needs, health, training history, and your own progress.
Do not extrapolate below age 60 or above 94. Changes to chair height, arm use, added weight, or duration make comparison inappropriate. Adapted assessments may still be useful when chosen by a professional.
Population, source access, and limits
The source labels its groups “Men” and “Women.” It does not explain how those categories were assigned or validated for every individual; you can choose not to compare. The worksheet does not report the derivation sample, recruitment, ethnic composition, or underlying statistical methods. These are clinical screening references, not modern nationally representative averages for all adults.