Body Recomposition Calculator

How body recomposition works

Body recomposition is the process of losing fat and adding muscle at the same time. The scale often stays flat because muscle and fat are being swapped pound-for-pound, but your shape, strength, measurements, and how clothes fit all shift. It is the most efficient outcome for beginners, returners, and anyone carrying higher body fat with room to add muscle.

Three levers do the work: a small calorie deficit (mostly on rest days), enough protein to keep building muscle, and progressive resistance training at least 3 to 5 days per week. Without the lifting stimulus, a deficit just turns into weight loss with muscle along for the ride. Without the protein, training stimulus has nothing to build with. Without the small deficit, fat barely moves.

How to use this calculator

Enter your sex, age, height, and weight. If you know your body fat percentage (DEXA, BodPod, or a recent caliper reading), add it: the calculator switches from Mifflin-St Jeor to Katch-McArdle, which is more accurate for leaner trainees because it anchors BMR to lean mass directly.

Pick your everyday activity level (outside the gym), how many days you lift per week, your training experience, and which way you want to bias the recomp: more fat loss, balanced, or more muscle gain. The results panel shows training-day calories, rest-day calories, the weekly average, and macro splits for each day type. Treat them as a 2 to 3 week starting point and adjust based on the mirror, the tape measure, and progress photos rather than weekly scale weight.

The math behind the numbers

BMR comes from Mifflin-St Jeor by default, or Katch-McArdle when body fat is entered. TDEE multiplies BMR by your activity factor (1.2 sedentary up to 1.725 very active). Training-day calories sit slightly higher than TDEE, rest-day calories sit lower, with the gap widening as you pick more aggressive fat-loss or muscle-gain emphasis.

Protein is set at roughly 1 gram per pound of lean body mass, which is the well-supported anchor for trainees in a deficit (ISSN position stand, Jäger et al. 2017). Fat is fixed at 30 percent of daily calories for hormonal health, and carbs fill the remainder. Realistic muscle gain rates come from Lyle McDonald\'s natural-trainee model: about 2 lb per month for new male lifters, 1 lb for women, dropping sharply with each year of training age. Fat loss for recomp is intentionally modest, around 0.5 to 1 percent of body weight per week, which preserves the muscle you are trying to build.

Track your recomp with a 75-day challenge

Recomp progress is invisible on the scale alone. The fix is to track multiple inputs: weigh-ins, monthly progress photos, waist and hip tape measurements, and strength on key lifts. A 75-day window is long enough to see real change without burning out on a strict cut. Reset75 handles the daily checklist, the photo log, and the measurement chart in one place, no account required.

Pair this calculator with the macro calculator for meal-planning detail, the calorie deficit calculator if you are biasing toward fat loss, and the 75 Soft tracker for a sustainable challenge structure that fits a recomp pace better than an aggressive cut.