performance math
The fitness numbers,
with the caveats.
Calculators across strength, endurance, body composition, and energy expenditure. Imperial or metric. The formula citations, population limits, and real-world variance most calculators skip.
Hero · Energy expenditure
TDEE & BMR calculator
Three BMR formulas side-by-side (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle). Calorie targets for cutting and bulking. With the activity-multiplier honesty most calculators skip.
Open calculator →Energy expenditure & macros
- TDEE & BMR calculatorthree BMR formulas, calorie targets, activity multiplier honesty
- Macro calculatorprotein/carb/fat targets from TDEE, ISSN-aligned, with a fibre target
- Protein calculatorgrams per pound by goal, ISSN ranges, lean-mass anchor on a cut
- Calorie deficit calculatordaily target, weekly loss, deficit as a share of maintenance, with the Hall 2011 long-term adjustment
- Weight loss rate calculatora sustainable loss rate as a percent of bodyweight (Helms 2014, Garthe 2011), the deficit it needs, and why a flat 1–2 lb/week is bodyweight-blind
- Caffeine dose calculatoryour ergogenic dose by bodyweight (3–6 mg/kg, ISSN 2021), with the fixed EFSA safety ceiling the per-kg dose can run past and the amount still on board at bedtime
- Walking calorie calculatorcalories burned per mile from your bodyweight and pace (Compendium METs), with the gross-vs-net split and why kcal/mile barely changes with pace in the normal range
- Running calorie calculatorcalories burned per mile from your bodyweight and pace (Compendium METs), with why a mile costs about the same at any running pace and running is only ~1.4× walking per mile, not the per-minute 2.8×
Strength training
- 1RM calculatorEpley, Brzycki, Lombardi, O'Conner, Mayhew side-by-side
- Percentage calculatorworking weights from your 1RM, plate math per side, and the percentage you actually lift after rounding
- Plate math calculatorbarbell loading per side with the plates you actually own, and the exact weight on the bar
- Wilks calculatorbodyweight-adjusted powerlifting score, the coefficient behind it, and where Wilks sits next to IPF GL and DOTS
- IPF GL calculatorthe Goodlift points that replaced Wilks for IPF competition, classic or equipped, with the category caveat
- Tonnage calculatorsession and weekly volume load from sets × reps × weight, with the intensity caveat raw tonnage hides
- RPE calculatorweight, reps and RPE into %1RM and an estimated max, with the RTS chart and the subjectivity caveat
Body composition
- Body fat calculatorNavy method, BMI, lean mass, with the measurement-error math
- Lean body mass calculatorBoer, James, Hume compared, with the James-reversal warning and the direct body-fat method
- FFMI calculatorfat-free mass index and normalized FFMI, with the body-fat error band and an honest read on the ~25 natural-limit claim
- BMI calculatorWHO categories, the weight at each category line for your height, with the muscular-athlete caveat
- Ideal weight calculatorDevine, Robinson, Miller, Hamwi compared, with the BMI healthy band overlaid
- Waist-to-hip ratio calculatorWHO 2008 cut-offs, with the tape-error band and the waist-circumference reading the ratio hides
- Waist-to-height ratio calculatorthe 0.5 rule and NICE bands, why one tape beats waist-to-hip ratio on error, and the height where the rule crosses a flat waist cut-off
Endurance & cardio
- Pace calculatorrace pace, splits, and speed in min/mi or min/km, with the cross-distance caveat
- Swim pace calculatorpace per 100 m or 100 yd, per-50, and even splits, with the exact yard-to-metre course conversion and the turns caveat most tools skip
- Heart rate zones calculatorTanaka HR_max, Karvonen reserve, 5-zone model, with the %HRmax-vs-Karvonen gap
- VDOT calculatorDaniels VDOT from a race, plus Easy/Marathon/Threshold/Interval/Rep paces, with what VDOT assumes
- Race time predictorpredict your time and pace at any distance from a race you've run (Riegel), with the distance range where it holds
- VO2 max calculatorCooper 12-min run and Rockport 1-mile walk in mL/kg/min, against Cooper Institute age/sex medians, with who each test is wrong for
- MAF heart rate calculatormaximum aerobic heart rate from the Maffetone 180 formula, with the cross-check that shows where it lands on the %HRmax zones
- Karvonen formula calculatorfive training zones from your heart rate reserve, with how much a resting-HR error costs and the exact gap above the %HRmax zones
- Resting heart rate calculatorread your RHR against both the conventional 60–100 band and Spodick's empirical 50–90, with the two-sided-low-reading caveat and the continuous mortality gradient (Zhang 2016) generic tools skip
- Running cadence calculatorstep and stride length from pace and cadence, plus the evidence-based +5–10% step-rate targets and why 180 spm was an elite-race observation, not a target
- Cycling FTP calculatorFunctional Threshold Power from a 20-minute test (the 0.95 rule) plus watts per kilogram, with the individual error band Borszcz 2018 measured on the estimate
- Cycling power zones calculatorall 7 Coggan zones in watts and W/kg from your FTP, with why Zone 7 has no ceiling and how the FTP error band moves every boundary
- Cycling calorie calculatorcalories from your average power and ride time (kilojoules ÷ gross efficiency), with the efficiency band the 1 kJ ≈ 1 kcal rule hides and why the number doesn't depend on bodyweight
Hydration
- Water intake calculatorhow much water to drink a day from the National Academies adequate intake, split into the ~20% from food and the ~80% you drink, plus sweat replacement (ACSM) — with the food/beverage split and the overdrinking caution generic tools skip
- Electrolyte calculatorsodium you sweat out in a session plus the daily sodium and potassium baseline, from the NASEM 2019 DRIs and Baker's sweat data — with the four-fold sweat-sodium range and the daily ceiling generic tools skip
Recovery & training load
- Sleep debt calculatorcumulative shortfall from your nightly need and the last 7 nights, split into hours short and hours banked — with why the net number is a floor, not a balance you clear with a weekend lie-in (Van Dongen 2003)
- HRV training calculatora week of morning readings into a personal baseline and decision band — your own smallest worthwhile change (0.5 × SD of ln rMSSD), not an age chart — with the parasympathetic-saturation caveat generic tools skip (Plews 2013)
About
Every calculator on performmath shows its math, names its primary citation, and includes a "when this calculator is wrong" section. We treat the fitness audience as capable of reading a study and benefiting from the population caveats most calculators skip. Calorie targets are math estimates, not medical advice — for medical conditions, eating disorders, or significant weight changes, consult a registered dietitian or physician.