Calculation Methodology

Every calculator on Calorie Deck is based on a published equation. This page lists each one, where it came from, and what it assumes. If you disagree with a result, the first thing to check is whether the underlying formula describes your situation at all.

Every formula we use

Body composition

Calculator	Formula	Source
BMI	weight (kg) ÷ height (m)²	WHO body mass index classification
Body fat (US Navy)	495 ÷ [1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)] − 450	US Navy circumference equations
Waist-to-height ratio	waist circumference ÷ height	Ashwell & Gibson boundary values
Ideal weight	Devine, Robinson and Hamwi equations from height and sex	Devine (1974); Robinson (1983); Hamwi (1964)

Energy expenditure

Calculator	Formula	Source
BMR and TDEE	Men 10W + 6.25H − 5A + 5 · Women 10W + 6.25H − 5A − 161, then × activity factor 1.2–1.9	Mifflin et al. (1990)
BMR from lean mass	370 + 21.6 × lean mass (kg)	Katch-McArdle equation
Calories burned by activity	kcal/min = MET × 3.5 × body weight (kg) ÷ 200	ACSM metabolic equation; MET values from the Compendium of Physical Activities
Steps to calories	steps × 0.0005 × body weight (kg) × pace factor	Step-based energy estimate, 0.762 m assumed stride

Nutrition targets

Calculator	Formula	Source
Protein	body weight (kg) × 1.2–2.2 g depending on activity and goal	ISSN position stand on protein and exercise
Macronutrient split	Protein set by body weight, fat at 25% of calories, carbohydrate fills the remainder	Standard sports nutrition practice; calories and protein dominate outcomes
Water intake	33 ml × body weight (kg) + 12 ml per minute of exercise + climate adjustment	Commonly cited hydration guidance
Caffeine ceiling	body weight (kg) × 3–6 mg, capped at 400 mg	FDA and EFSA adult guidance of 400 mg per day

Heart rate and training

Calculator	Formula	Source
Maximum heart rate	208 − 0.7 × age (Tanaka); 220 − age (traditional); 206 − 0.88 × age (Gulati)	Tanaka, Monahan & Seals (2001); Gulati et al. (2010)
Target heart rate	resting HR + (max HR − resting HR) × intensity	Karvonen heart rate reserve method
One-rep max	Epley, Brzycki and Lander equations	Epley (1985); Brzycki (1993); Lander (1985)
Pace	total time ÷ distance	Standard race-pace conversion

Sleep

Calculator	Formula	Source
Sleep cycles	90-minute cycles with a 15-minute sleep-onset buffer	Basic rest-activity cycle model of sleep

What we do and do not claim

We claim that these equations are implemented correctly and that the sources shown are the real sources. We do not claim that any of them accurately predicts your individual physiology.

That distinction matters more than it sounds. A correctly implemented equation can still be a poor model for a particular person — a muscular athlete, an older adult, someone on medication that alters heart rate. Each calculator page states where its formula tends to break down.

How results are checked

Each formula is implemented once and reused across pages, so there is one place to verify.
Outputs are spot-checked against hand calculation and published worked examples.
Input limits are set to the ranges the source studies actually covered.
Unit conversions (metric and imperial) are checked to produce identical results either way.

What this site is not

Calorie Deck is an independent reference project. It is not a medical device, it does not diagnose, and it is not a substitute for professional advice. No result here has been reviewed by a clinician, and we do not present it as though it has been.

If you find an error in a formula or its implementation, please tell us. Corrections are published on this page with the date of the change.