All calculators

Every performmath calculator, grouped by what you're trying to measure. Each one shows its formula, cites a primary source, and has a "when this calculator is wrong" section.

Energy expenditure & macros

• TDEE & BMR calculatorthree BMR formulas, calorie targets, activity multiplier honesty
• Calorie deficit calculatordaily intake target, weekly loss, the deficit as a share of maintenance, and where the 3,500-kcal rule stops holding
• Weight loss rate calculatora target loss rate set as a percent of bodyweight (Helms 2014 / Garthe 2011) rather than a flat 1–2 lb/week, the daily deficit it needs, and the band that holds muscle — with the fixed-percent timeline that slows as you lighten
• Walking calorie calculatorcalories burned walking a mile from your bodyweight and pace, using the 2011 Compendium walking METs and the ACSM kcal formula — with the two things generic tools skip: gross vs net (a MET already counts the resting calories you'd spend anyway, so the walk's own share is only (MET − 1)/MET, about 71% at 3.0 mph), and the fact that kcal/mile is a shallow U in pace, ~100 at 3.0 mph for a 180 lb walker but higher at both a 2.0 mph dawdle and a 4.5 mph near-jog
• Running calorie calculatorcalories burned running a mile from your bodyweight and pace, using the 2011 Compendium running METs and the ACSM kcal formula — with the two things generic tools skip: per mile the cost is nearly flat and even drifts down with pace (~140 kcal/mile at 6 mph to ~122 at 9 mph for a 180 lb runner), so "run faster to burn more per mile" is false; and running is only ~1.4× walking per mile (gross), not the per-minute 2.8× that most comparisons quote

Macros & nutrition

• Macro calculatorprotein/carb/fat from TDEE, protein per pound, with a fibre target
• Protein calculatordaily protein by goal (ISSN bands), lean-mass anchor on a cut, with the muscle-gain ceiling
• Caffeine dose calculatoryour ergogenic caffeine dose from bodyweight (3–6 mg/kg, ~60 min pre-exercise, ISSN 2021), with the two things the flat mg/kg tools skip: the EFSA safety ceiling is a fixed 400 mg/day the per-kg dose can run straight past for a heavier athlete, and the ~5-hour half-life leaves an evening dose still on board at bedtime

Strength training

• 1RM calculatorfive formulas side-by-side (Epley, Brzycki, Lombardi, O'Conner, Mayhew), honest about the rep range
• Percentage calculatorworking weights from a 1RM at every training percentage, each rounded to a loadable weight with plates per side, plus the percentage you actually lift after rounding
• Plate math calculatorplates to load per side for any target, the exact weight on the bar, and the closest you can build with only the plates you own, in lb or kg
• Wilks calculatora powerlifting total turned into a bodyweight-adjusted score, with the coefficient behind it and where Wilks sits next to the IPF GL points that replaced it
• IPF GL calculatorthe Goodlift points that replaced Wilks for IPF competition in 2020, classic or equipped and full power or bench, with the exponential-vs-polynomial difference and why a GL score only compares within its category
• Tonnage calculatorsets × reps × weight summed across a session, with a week-over-week delta and the reason raw tonnage isn't the metric muscle growth is built on — hard sets per muscle per week is
• RPE calculatora set's weight, reps and RPE turned into the %1RM it represented and an estimated max, on the Tuchscherer RTS chart, with the reps-in-reserve subjectivity caveat and the plate-rounding step most tools skip

Body composition

• Body fat calculatorNavy method + BMI + lean mass, with the measurement-error and Katch-McArdle context
• BMI calculatorWHO categories, the weight at each category line for your height, and the muscular-athlete caveat worked out
• Ideal weight calculatorDevine, Robinson, Miller and Hamwi side by side, the drug-dosing origin most tools skip, and the BMI healthy band overlaid
• Lean body mass calculatorBoer, James and Hume side by side, a warning when the James formula runs backwards at high weight, and the direct body-fat method Katch-McArdle uses
• FFMI calculatorfat-free mass index and normalized FFMI from weight, height and body fat, with the body-fat error band and why the ~25 natural ceiling is a male-sample bound, not a wall
• Waist-to-hip ratio calculatorthe ratio against the WHO 2008 cut-offs, the tape-error band a slip of the measure puts on it, and the waist-circumference reading the ratio hides in its denominator
• Waist-to-height ratio calculatorthe waist against the 0.5 boundary and the NICE bands, why one variable tape beats waist-to-hip ratio on measurement error, and the exact height where the 0.5 rule crosses a flat waist cut-off

Endurance & cardio

• Pace calculatorpace, time, distance, speed and even splits in min/mi or min/km, with why one pace can't cross race distances
• Heart rate zones calculatorfive zones by %HRmax and by Karvonen reserve, Tanaka/Fox/Gulati max HR, with the error band and the two-method gap
• VDOT calculatorDaniels VDOT from a race and the five training paces (E/M/T/I/R) in min/mi or min/km, with what VDOT assumes and where Easy and Rep are ranges, not points
• Race time predictorpredicted finish time and pace at any distance from a race you've run (Riegel's 1.06 formula), in min/mi or min/km, with the distance ratio flagged and whether the prediction is reliable or an extrapolation
• VO2 max calculatorestimate VO2 max from a 12-minute run (Cooper 1968) or a one-mile walk (Kline 1987) in mL/kg/min, placed against Cooper Institute age and sex medians, with who each field test is wrong for
• MAF heart rate calculatormaximum aerobic heart rate from the Maffetone 180 formula with all four adjustments, cross-checked against the ACSM %HRmax zones so you can see the MAF ceiling lands in Zone 3, not Zone 2, and the medication caveat done as a clinician question
• Karvonen formula calculatorfive training zones from your heart rate reserve (Karvonen 1957) using a measured or estimated max (Tanaka/Fox-Haskell), quantifying how much a resting-HR measurement error moves the target and the exact bpm gap the %HRR zones sit above the plain %HRmax zones
• Running cadence calculatorstep length and stride length from your pace and cadence via the kinematic identity, with the evidence-based +5–10% step-rate targets (Heiderscheit 2011) computed from your own baseline and the honest origin of the 180 spm number — Daniels' 1984 Olympic count of 46 elite racers, not a universal target
• Cycling FTP calculatorFunctional Threshold Power from a 20-minute test (Allen & Coggan's 0.95 rule) or a full 60-minute test, plus watts per kilogram — with the individual error band Borszcz 2018 measured on the estimate (mean bias only −1 to −5 W but limits of agreement up to −62 to +60 W) and why W/kg, not raw watts, is the number that compares riders and governs climbing
• Cycling power zones calculatorthe 7 Coggan power zones — Active Recovery through Neuromuscular Power — in watts and watts per kilogram from your FTP, with two things the generic calculators skip: Zone 7 (Neuromuscular Power) is not a percentage band of FTP, so we print no watt ceiling for it, and because every boundary is a fixed multiple of FTP, the 20-minute test's individual error band (±40–60 W, Borszcz 2018) carries straight through to every zone edge
• Swim pace calculatorpace per 100 and per 50 from a distance and time, in metres or yards, with even splits at each pool wall — plus two things generic swim tools skip: the exact yard-to-metre conversion (100 yd = 91.44 m, so a per-100 m pace is always the slower-looking clock), and the reason a distance-converted pace overstates a short-course swim, because a 25-length pool has twice the push-off walls of a 50-length pool
• Resting heart rate calculatormeasure and interpret your resting heart rate against both the conventional clinical band (60–100 bpm) and the empirical range a primary paper derived (Spodick 1992, 50–90 bpm), with two things the generic tools skip: a low reading is a two-sided signal — training bradycardia (ACSM) or a beta-blocker/conduction problem, opposite meanings from the same number — and the mortality risk inside "normal" is a continuous gradient, about 9% higher all-cause mortality per 10 bpm (Zhang 2016), not a pass/fail box
• Cycling calorie calculatorcalories burned cycling from your average power and ride time — the power-meter method, work in kilojoules (avg watts × seconds ÷ 1000) divided by gross efficiency — with two things generic tools skip: the "1 kJ ≈ 1 kcal" shortcut is an efficiency assumption, not a law (kJ equals kcal exactly at 23.9% gross efficiency, and measured cycling efficiency runs ~20–25%, so a 720 kJ ride is 688 kcal at 25% but 860 at 20% — the honest output is a band), and the calorie figure is bodyweight-independent because it depends only on work and efficiency, so a 60 kg and a 90 kg rider at the same power for the same time burn the same calories and differ only in W/kg

Hydration

• Water intake calculatorhow much water to drink a day from the National Academies adequate intake (3.7 L men / 2.7 L women, IOM 2004), split into what comes from food (~20%) and what you actually drink (~80%), plus sweat replacement from the ACSM 0.5–2.0 L/h range — with the two things generic tools skip: the food-vs-beverage split that makes their headline a fifth too high, and the reminder that the IOM set an adequate intake, not a bodyweight requirement, so drinking past your sweat rate risks hyponatremia
• Electrolyte calculatorthe sodium you sweat out in a session (sweat volume × whole-body sweat sodium, Baker 2016 mean 35.9 mmol/L, range 18.2–70.8) plus the daily sodium and potassium baseline (NASEM 2019: sodium AI 1,500 mg, CDRR ceiling 2,300 mg, potassium 3,400 mg men / 2,600 mg women) — with the two things generic tools skip: the daily sodium DRI is a ceiling to stay under, not a target to top up with tablets, and sweat sodium varies about four-fold between people, so the honest output is a band and a long hot session can lose more sodium than the whole day's ceiling

Recovery & training load

• Sleep debt calculatorcumulative sleep debt from your nightly need (7–9 h for adults, Hirshkowitz 2015) and the last 7 nights, with two things the trackers skip: the net figure is split into the hours you fell short and the hours you banked, and the recovery-realism caveat that makes the net a floor, not a balance — recovery sleep only partially reverses a chronic deficit (Van Dongen 2003; Depner 2019), and under chronic restriction alertness plateaus while performance keeps sliding, so "I feel fine" isn't the all-clear
• HRV training calculatorturn a week of morning HRV readings (rMSSD) into a personal baseline and decision band, then score today's reading, with two things the generic tools skip: the threshold is your own smallest worthwhile change — 0.5 × the SD of your ln rMSSD (Hopkins 2000; Plews 2013), the individual band the guided-training trials used (Vesterinen 2016) — not an age/sex chart or a flat 10% rule, because between-person HRV varies several-fold; and higher is not automatically better, since at high loads ln rMSSD can fall while vagal tone rises (parasympathetic saturation, Plews 2013/2017)