This page explains exactly how the calculator produces its numbers and how we write and check our articles.
Step 1: BMR formulas
| Formula | Equation (W = kg, H = cm, A = years, BF = body fat %) | Source |
|---|---|---|
| Mifflin-St Jeor (default) | Men: 10W + 6.25H − 5A + 5; Women: 10W + 6.25H − 5A − 161 | Mifflin et al., 1990 |
| Revised Harris-Benedict | Men: 88.362 + 13.397W + 4.799H − 5.677A; Women: 447.593 + 9.247W + 3.098H − 4.330A | Roza & Shizgal, 1984 |
| Katch-McArdle | 370 + 21.6 × W × (1 − BF/100) | McArdle, Katch & Katch, Exercise Physiology |
We use Mifflin-St Jeor by default because a 2005 systematic review (Frankenfield et al.) found it the most reliable of the common equations for healthy adults.
Step 2: Activity factors
| Level | Factor |
|---|---|
| Sedentary | 1.2 |
| Lightly active | 1.375 |
| Moderately active | 1.55 |
| Very active | 1.725 |
| Extra active | 1.9 |
These are the activity multipliers widely used with BMR equations. They cover exercise, daily movement and digestion together.
Step 3: Goal adjustments
We use the common estimate of about 7,700 kcal per kg of body weight change (3,500 kcal per lb). Losing 0.5 kg a week ≈ 550 kcal a day below TDEE. This estimate works best over weeks, not years; see the 3,500-calorie rule.
We do not show targets below 1,200 kcal (women) or 1,500 kcal (men).
Step 4: Macros
- Protein: 1.6 g per kg of body weight (within the ISSN range of 1.4–2.0 g/kg for exercising people).
- Fat: 25% of calories (within the Institute of Medicine range of 20–35%).
- Carbohydrate: remaining calories.
- Energy values: protein and carbohydrate 4 kcal/g; fat 9 kcal/g; 1 kcal = 4.184 kJ.
Limits
- Formulas are for healthy adults aged 18–80.
- They do not apply to pregnancy, breastfeeding, or many medical conditions.
- Individual results can differ by 10% or more.
How we write and check content
- Every article cites published research or official guidance, linked at the end.
- Every number and worked example is recalculated before publishing.
- Articles show a “last updated” date and are reviewed at least once a year, or when guidance changes.
- Health topics that need clinical judgement (for example pregnancy) are reviewed by a qualified professional, named on the article.
- We correct errors when readers report them. Contact us.
Sources
- Mifflin MD, et al. (1990). Am J Clin Nutr 51(2):241–247. https://pubmed.ncbi.nlm.nih.gov/2305711/
- Roza AM, Shizgal HM (1984). Am J Clin Nutr 40(1):168–182. https://pubmed.ncbi.nlm.nih.gov/6741850/
- Frankenfield D, et al. (2005). J Am Diet Assoc 105(5):775–789. https://pubmed.ncbi.nlm.nih.gov/15883556/
- Jäger R, et al. (2017). J Int Soc Sports Nutr 14:20. https://jissn.biomedcentral.com/articles/10.1186/s12970-017-0177-8
- Institute of Medicine (2005). Dietary Reference Intakes for Energy… https://nap.nationalacademies.org/catalog/10490
- Hall KD, et al. (2011). Lancet 378:826–837. https://doi.org/10.1016/S0140-6736(11)60812-X
Who builds and checks the calculator
The calculator was built and tested by Zeeshan Nawaz, Calculator Developer at Tuff Search. He also writes and fact-checks the guides on this site. Each tool is based on published formulas and official sources, and is checked against worked test cases before it goes live.