Formulas and Sources

Every number on this site and in the app comes from a published equation or guideline. This page lists them all, with the research behind them, so you can check our work.

By Syed Sibt Ul Hassan, updated 20 October 2026.

Resting energy (BMR)

Weight in kg, height in cm, age in years. Lean body mass = weight × (1 − body fat % ÷ 100).

We default to Mifflin-St Jeor because a systematic review found it predicted resting metabolic rate within 10% of measured values in more non-obese and obese adults than other common equations. The lean-mass equations are offered when you enter a body fat percentage.

Daily energy (TDEE) and goals

TDEE = BMR × activity factor

Goal targets are percentages of TDEE: lose fast −25%, lose −20%, lose slowly −15%, maintain 0%, lean gain +5%, gain +10%, gain fast +15%. Estimated weekly change uses 7,700 kcal per kg (about 3,500 kcal per lb), a simplification that overstates long-term change because the body adapts. We warn when a target falls below 1,200 kcal (women) or 1,500 kcal (men) a day, or when a plan loses more than 1% of body weight a week.

Goal planner: daily calories = TDEE ± pace (kg/week) × 7,700 ÷ 7; weeks = |goal − current| ÷ pace

Measured TDEE in the app

Measured TDEE = average daily intake − (weight slope per day × 7,700)

Over the last 28 days, the app fits a least-squares line through your weigh-ins (so water swings average out) and averages your logged intake, leaving out today because the day isn’t finished. It needs a span of at least 14 days, 10 weigh-ins and 10 days of food. This is the same energy-balance principle used in research on body weight change.

Macros and protein

Protein and carbohydrate count as 4 kcal per gram, fat as 9 kcal per gram.

If protein leaves no room for carbs, carbs are set to 0 g and fat fills the rest. Daily protein ranges by goal: general health 0.8 to 1.0 g/kg, endurance 1.2 to 1.6, age 65+ 1.0 to 1.2, muscle gain or fat loss with strength training 1.6 to 2.2. With a BMI of 30 or more, protein uses the weight at BMI 25 for the person’s height.

BMI, ideal weight and body fat

BMI = weight (kg) ÷ height (m)² Healthy weight range = 18.5 × m² to 24.9 × m²

Categories follow the WHO: below 16 severely underweight, below 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, 30 and above obesity. We note that health risks for many Asian adults rise from a BMI of about 23 (WHO expert consultation, 2004).

Ideal weight (per inch over 5 ft): Devine: men 50 kg + 2.3 kg, women 45.5 kg + 2.3 kg; Robinson: men 52 + 1.9, women 49 + 1.7; Miller: men 56.2 + 1.41, women 53.1 + 1.36; Hamwi: men 48 + 2.7, women 45.5 + 2.2.

U.S. Navy body fat (cm): Men: 495 ÷ (1.0324 − 0.19077 log10(waist − neck) + 0.15456 log10(height)) − 450 Women: 495 ÷ (1.29579 − 0.35004 log10(waist + hip − neck) + 0.22100 log10(height)) − 450

Body fat categories (American Council on Exercise). Men: essential below 6%, athletic 6 to 13%, fit 14 to 17%, average 18 to 24%, above average 25%+; women: below 14%, 14 to 20%, 21 to 24%, 25 to 31%, 32%+.

Water

Water (L) = 0.033 × weight (kg) + activity extra (0, 0.35, 0.5, 0.75 or 1.0 L)

General guidance for healthy adults, in line with the EFSA adequate intakes of about 2.0 L (women) and 2.5 L (men) of total water a day.

Exercise calories (GPS workouts in the app)

Active calories = (MET − 1) × weight (kg) × moving hours

MET values for walking, running and cycling come from the 2011 Compendium of Physical Activities and are interpolated by speed. We subtract 1 MET so resting energy isn’t counted twice.

Food data

The app’s 356 built-in foods use typical recipes and portion sizes; their values are estimates. Barcode data comes from Open Food Facts, available under the Open Database License (ODbL). AI photo estimates are a starting point that you check and edit before adding.

How we check the math

The website and the app use the same calculation file, so a number here is the same number in the app. It is covered by automated tests that compare results against worked examples (for example, Mifflin-St Jeor for a 30-year-old, 175 cm, 80 kg man = 1,748.75 kcal), and every change is tested before release. Found something that looks wrong? Email info@tdeecalculatornet.net and we will fix errors quickly and update the date at the top of this page.