Body Recomposition Calculator

Body recomposition is the process of changing the balance between your lean mass and your body fat, rather than simply moving a number on the scale. In practice that usually means reducing body fat while keeping, or ideally adding, lean mass. That is what body recomposition means in fitness: a shift in body composition, not a big change in body weight.

It is useful because muscle and fat do not weigh the same. A kilogram of muscle is far denser than a kilogram of fat, so a person can lose a noticeable amount of fat, gain some lean mass, and finish at almost exactly the body weight they started at. That is why progress during recomposition is often hard to see on the scale alone, and it is why the calculator below focuses on calories and protein rather than promising a rate of change.

If you do not have a body-fat estimate, the body fat calculator can give you a starting figure, and the lean body mass calculator turns that figure into lean and fat mass you can track.

Recomposition works on two sides at the same time. Resistance training supplies the reason for your body to keep muscle, and a modest calorie deficit creates the energy gap that allows fat to come off. Neither side works well alone: calories without training tend to lose muscle along with fat, and training without a deficit mostly builds strength with little change in fat mass.

• Progressive resistance training2–4 sessions per week
• Protein1.6–2.0 g per kg
• CaloriesModest deficit
• RecoverySleep and rest days

Individual results differ a great deal, mainly because of training status, starting body composition, protein intake and consistency. Someone lifting for the first time usually notices more change than someone who has trained hard for years, and anyone eating poorly will struggle no matter what the numbers say.

The calculator works from your maintenance calories, which come from the Mifflin-St Jeor equation and your activity level, then applies one documented adjustment: 10% below maintenance. It does not ask for a weight-loss rate, because a rate-based target is the wrong tool for recomposition.

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age ± constant

TDEE = BMR × activity multiplier

Recomposition target = TDEE − 10%

That 10% is a transparent, documented planning assumption rather than a physiological constant. It is deliberately modest: a larger deficit is harder to sustain, takes more out of your training, and is not automatically better for holding on to muscle. It is not zero either, because most people doing recomposition do want some fat loss.

Compare it with the calorie deficit calculator, which lets you pick a weekly weight-loss rate and can reach roughly 1,100 kcal a day, or the calorie surplus calculator for the opposite direction. For maintenance calories on their own, use the TDEE calculator or the calorie calculator.

Your actual energy needs shift with training, sleep, stress and activity, and the activity multiplier is the least precise part of any estimate like this. Treat the result as a starting number to adjust from over a few weeks rather than as a prescription.

Protein is the part of recomposition people most often get wrong. In a calorie deficit, protein helps you hold on to lean mass while fat comes off, which is exactly what recomposition depends on. The calculator reuses the protein calculator and applies its existing "lose" goal of1.6–2g per kg of body weight per day: the same range that tool gives for higher protein to help preserve muscle in a deficit.

Individual protein requirements differ. A larger person generally needs more in total grams, and some people respond better to the upper or lower end of the range, so treat the target as a planning number rather than a requirement. To work out the rest of your intake, the macro calculator can turn a calorie target into carbohydrate, fat and protein splits.

A body recomposition diet is not a special diet. It is an ordinary, sustainable way of eating that happens to sit slightly below maintenance, with enough protein and enough food to train on. There is no need to restrict yourself to a handful of foods, and extreme approaches usually backfire because they are hard to hold for long enough to see a result.

• Protein, spread across the day3–4 servings
• Vegetables and fruit for volume and fibreMost meals
• Carbohydrate sources around trainingRice, oats, potatoes
• Fat sources for balanceOlive oil, nuts, seeds

Eating enough carbohydrate matters more than people expect, because it fuels the lifting that keeps your muscle. A recomposition diet that strips out carbohydrates tends to hurt training quality, and fat is easier to hit in a deficit when some of the remaining calories come from it. Whatever you choose, aim for an eating pattern you can keep up for months rather than weeks.

Resistance training is the single most important part of a body recomposition workout plan. Calories decide the direction of travel; training decides how much of the muscle you already have you keep, and whether you add more.

• Train each muscle group2+ times per week
• Progress the load over timeThe point of the plan
• Enough protein to support adaptation1.6–2.0 g per kg
• Sleep7–9 hours

If you want a structured programme to follow, start with a full-body routine done two or three times a week and add weight or reps to your main lifts over time. Keep realistic expectations: recomp is a slow process measured in months, and a program that leaves you exhausted for a week will not outrun one you can actually sustain.

The principles are the same for men and women: resistance training, adequate protein, a modest calorie adjustment and consistency. What differs is that the underlying numbers differ, which is exactly what the calculator accounts for by using the female Mifflin-St Jeor constant. Your calorie and protein needs are individual, and there is no reason to assume a generic aggressive deficit is required to make progress.

One practical difference worth knowing: body weight often moves around across a menstrual cycle, from water retention and changes in gut contents, and hormonal contraception can add to that. A single weight reading tells you very little, so judge progress on a trend over several weeks rather than on this morning's number, and consider measurements and how training feels as well.

If you are pregnant or breastfeeding, or managing an eating disorder or a health condition, get individual guidance from a doctor or registered dietitian before deliberately changing your calories or protein intake.

Body recomposition for men follows the same approach: train hard, eat enough protein, and hold a modest deficit rather than an aggressive one. The calculator uses the male Mifflin-St Jeor constant, which is why the same age, height, weight and activity level produces different maintenance calories here than it does for a woman.

Individual needs still vary a great deal. Men who carry more body fat usually have more fat mass to lose and may find the adjustment easier to tolerate; men who already train heavily often need to watch recovery and protein more than they watch calories. The macro calculator is useful if you want to see how your calories and protein fit into a full breakdown.

There is no universal timeline, and any tool that gives you a fixed number of weeks is guessing. How long body recomposition takes depends on your training status, your starting body composition, how well you execute the nutrition, how well you recover, and above all how consistent you are. A beginner and a well-trained lifter on identical numbers will get different results.

Progress is also usually gradual and often not visible on the scale, because fat loss and lean mass gain partly cancel each other out. Judge it over a period of months. If you are still seeing the scale move quickly downward after several weeks, the deficit is probably larger than recomposition needs, and both recovery and lean mass are likely suffering.

Yes. Recomposition is a real, well-documented phenomenon, and the research on it is considerably stronger than it was a decade ago. But the honest answer to "is body recomposition real" is that the mechanism is real while the effect size is individual: how much fat you lose and how much muscle you gain or keep at the same time varies considerably from person to person.

Is body recomposition possible? For beginners, for people returning after a break, and for people carrying more body fat, it is often quite achievable. For experienced lifters who are already near their limits, it is possible but slower and smaller. Training status matters, energy balance matters, protein matters, and none of it is guaranteed. Being honest about that is the difference between a useful starting point and a promise nobody can keep.

A person can lose fat, gain lean mass, and finish at essentially the same scale weight as before. That is not a contradiction: muscle is denser than fat, so a change in composition often shows up as a similar weight with a different shape. It is also why judging recomposition by body weight alone will convince you that nothing is happening when something is.

Track other things too:

• Waist measurementWeekly, same time of day
• Progress photosSame light, same angle
• Strength trendsLifts going up over time
• Body-weight trendWeekly average, not one reading

Consumer body-composition scales and calipers are rough tools, not precision instruments, so do not treat a single reading as truth. Small day-to-day changes in either direction are usually measurement noise and normal fluctuation, which is exactly why trends beat single numbers.

Everything this calculator produces is an estimate and a starting point, not a prediction. The energy equation is a population average, the activity multiplier is a rough guess, and your real needs change from day to day. Body composition changes are individual too: no formula can tell you how many kilos of muscle you will gain or how many kilos of fat you will lose, and nothing here promises results in a fixed number of weeks.

This is a general estimation tool, not medical advice. It is not intended to set nutritional targets for pregnancy, breastfeeding, eating-disorder recovery, or any medical condition that needs supervised nutrition. If any of those apply, or you simply want a plan that accounts for your circumstances, speak with a doctor or registered dietitian before deliberately changing your calorie intake. If a target would fall below this calculator's 1,200-calorie floor, it is not shown at all.