Body Recomposition Calculator
Get your daily calorie and protein targets for losing fat, recomposition, or building muscle, based on the highest quality published research.
Recomposition calculator
Estimate the calories you burn each day using the Institute of Medicine equations, which have tracked most closely with doubly labeled water, the gold standard for measuring energy expenditure in daily life. Then get calorie and protein targets for your goal.
Calibrate with your own weight trend
Every equation is an estimate. After 2 to 4 weeks of steady eating, your scale is more accurate than any formula. Weigh yourself each morning, compare weekly averages rather than single days, and enter what you find.
Your measured maintenance
Uses about 3,500 kcal per pound (7,700 kcal per kg) of weight change. That figure is an approximation, which is why longer tracking periods are more reliable.
How this calculator works
Calories burned in daily life are measured with doubly labeled water. Resting expenditure is measured with indirect calorimetry. Everything else, including this tool, is an estimate. Good prediction equations land within about 10% of measured values for roughly 7 in 10 people, and individual errors of several hundred calories a day are common.
Among the options studied against doubly labeled water, the Institute of Medicine Dietary Reference Intake (IOM/DRI) total energy expenditure equations with a physical activity level have shown the lowest bias, including in adults with overweight or obesity and in older adults. That is the primary estimate here. Most online calculators instead use the Mifflin St Jeor resting equation multiplied by an activity factor, so we show that result as a cross-check.
Equations used
What we leave out on purpose
We don't ask for body fat percentage. In validation studies, adding body composition did not meaningfully improve accuracy, and home body fat estimates add their own error.
How targets are set
Fat loss uses a 20% deficit, recomposition a 10% deficit, and muscle gain a 10% surplus. Protein ranges from 1.6 to 2.2 g per kg, toward the higher end during a deficit, consistent with meta-analytic evidence on protein and resistance training. Above a BMI of 30, protein is calculated from a reference weight, since needs track lean mass rather than total weight. Calorie targets never go below 1,500 for men or 1,200 for women.
Where estimates are weaker
These equations are built for adults 19 and older. Newer age specific equations may perform better after 65. They are not designed for pregnancy, breastfeeding, high volume endurance athletes, or medical conditions that change metabolism.
References
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: National Academies Press; 2005.
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789.
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.
For education only. Arete Health provides coaching, not medical care, and this tool does not diagnose or treat any condition. If you are pregnant, breastfeeding, managing a medical condition, or have a history of disordered eating, talk with your clinician before changing how you eat.
Created by Mahiar Rabie, MS, MD using the current, highest quality evidence available. For healthy adults. Educational only, not medical advice.