How we calculate your targets

Reviewed: August 2026
Your numbers aren't a guess. Here's the exact math and the research behind it.
Resting calorie burn (BMR)
We estimate the calories your body burns at rest from your sex, weight, height, and age using the Mifflin-St Jeor equation — the formula most widely validated against measured resting energy expenditure.
Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990;51(2):241–247.
https://doi.org/10.1093/ajcn/51.2.241
Total daily calorie burn (TDEE)
Your BMR is scaled up by an activity multiplier (1.2–1.725) based on how much you move and train, following the physical activity level bands used in international energy-requirement guidelines.
Food and Agriculture Organization of the United Nations / World Health Organization / United Nations University. "Human Energy Requirements: Report of a Joint FAO/WHO/UNU Expert Consultation." FAO Food and Nutrition Technical Report Series, 2001.
https://www.fao.org/4/y5686e/y5686e00.htm
Calorie surplus for muscle gain
We add a surplus on top of your maintenance calories, sized down as training experience goes up: beginners convert a larger surplus into muscle ('newbie gains'), while advanced lifters build muscle more slowly and need a tighter surplus to stay lean.
Iraki J, Fitschen P, Espinar S, Helms E. "Nutrition Recommendations for Bodybuilders in the Off-Season: A Narrative Review." Sports, 2019;7(7):154.
https://doi.org/10.3390/sports7070154
Daily protein target
Protein is set at 0.9g per lb of bodyweight — the middle of the 0.8–1.0g/lb range shown to support muscle growth in people who lift.
Jäger R, Kerksick CM, Campbell BI, et al. "International Society of Sports Nutrition Position Stand: protein and exercise." Journal of the International Society of Sports Nutrition, 2017;14:20.
https://doi.org/10.1186/s12970-017-0177-8
These are general fitness and nutrition estimates, not medical advice. Talk to a doctor or registered dietitian before making major changes to your diet, especially if you have a medical condition.
Run these formulas yourself in the lean bulk calculator →