Fitness & Performance
Every fitness & performance calculator on CalcEngines — each with its formula, a worked example, the standard it follows and the assumptions it makes.
3 calculators in this section
- One Rep Max Calculator (7 Formulas, Epley, Brzycki)Seven published one-repetition-maximum formulas from one set of inputs — Epley, Brzycki, Lombardi, O’Conner, Wathen, Mayhew and Lander — with the spread between them printed as an output rather than hidden behind whichever one a page happens to have chosen. That spread is about 5.6% of the lowest estimate at seven repetitions, 7.8% at ten, 24.9% at fifteen and 57% at twenty, so the number of repetitions you did decides how much the choice of formula matters. This page exists so that nobody has to attempt a true one-repetition maximum to get a figure, and it says plainly what each formula does at the edges where it stops working.
- Target Heart Rate Zones Calculator (5 Zones, bpm)Every heart rate zone on every watch and every chart rests on two guesses stacked on top of each other: an equation that predicts your maximum heart rate from your age, and a rule that turns a percentage into a number of beats. This page prints five published maximum equations together — Fox’s 220 − age, Tanaka 2001, Gellish 2007, Nes 2013 and Astrand — and computes every zone BOTH as a percentage of maximum AND by Karvonen’s heart rate reserve, because those two rules routinely put the same zone in windows that do not overlap. The published standard deviation of an age-predicted maximum is 10 to 12 beats a minute, so the spread is printed as an output rather than mentioned in a footnote.
- VO2 Max Calculator (Cooper, Rockport, Uth)Three published field estimates of maximal oxygen uptake, computed together from one set of inputs — Cooper’s 12-minute run (1968), the Rockport one-mile walk (Kline 1987) and Uth’s heart rate ratio method (2004) — each with the error its own authors published: ±5.0 mL/kg/min for Rockport, a 3.0 mL/kg/min overestimate with limits of agreement of 0.10 to 5.94 for Cooper in one Indian validation, and a constant Uth derived in well-trained men only. They are not interchangeable and this page does not average them. It prints all three, the spread between them, and where each one lands against published population means by age and sex.