The math of health: calories, energy use and heart rate
Health calculators run on a few published equations. These pages show the equations, where they came from and how far to trust the output. They explain; they do not diagnose or prescribe.
4 pages in this section
- GuideHow to Calculate TDEE (Total Daily Energy Expenditure)TDEE is resting energy times an activity factor. The Mifflin-St Jeor step, five multipliers, a worked example, a calculator and how big the error is.
- ReferenceResting metabolic rate formulas comparedThe resting metabolic rate formulas side by side: coefficients, who each was built on, worked example and how far they disagree and miss.
- ReferenceMaximum Heart Rate Formula: 220 − Age and Better OptionsThe maximum heart rate formulas compared: 220 minus age, Tanaka, Gellish, Nes and Gulati, with population, error, an age table and worked example.
- ReferenceSleep Cycle Calculator Math: How the 90 Minute Rule WorksSleep cycles average 90 minutes, so bedtime math is subtraction. See the formula, bedtime tables, a cosine model, and why cycles vary from 60 to 110 minutes.