Body Recomposition Calculator

About the Body Recomposition Calculator

Body recomposition — "recomp" for short — means changing what your body is made of rather than just what it weighs: losing fat while keeping or building muscle. Because muscle is being kept or added, the scale is a poor guide to progress. What matters is the split between fat mass and lean mass, and the weight you will reach at the body fat percentage you are aiming for.

This body recomposition calculator splits your current weight into fat and lean mass from your body fat percentage, then works out your goal weight at a target body fat percentage — keeping your lean mass the same, or after a lean mass gain you expect. It shows how much fat you need to lose, the change on the scale, and a rough timeline.

How to Use the Body Recomposition Calculator

Enter your current weight and choose kg or lb.

Enter your current body fat percentage, from a smart scale, callipers or a tape measure formula.

Enter your target body fat percentage.

Optionally, enter the lean mass you expect to gain, or a negative number for a loss.

The Formula

  fat mass     = weight × body fat %
  lean mass    = weight − fat mass
  goal weight  = (lean mass + lean mass change) ÷ (1 − target body fat %)
  fat to lose  = current fat mass − goal fat mass

Step-by-Step Examples

85 kg at 25% body fat, aiming for 15%.

  fat mass     85 × 0.25 = 21.25 kg
  lean mass    85 − 21.25 = 63.75 kg
  goal weight  63.75 ÷ (1 − 0.15) = 75 kg
  fat to lose  10 kg

At about 0.5 kg of fat a week, that takes roughly 20 weeks.

The same person, also gaining 3 kg of lean mass.

  new lean mass  63.75 + 3 = 66.75 kg
  goal weight    66.75 ÷ 0.85 = 78.5 kg
  fat change     −9.5 kg, weight change −6.5 kg

The scale shows only 6.5 kg lost, even though almost 10 kg of fat has gone.

In pounds: 200 lb at 25% body fat has 150 lb of lean mass; at 15% the goal weight is 150 ÷ 0.85 = 176.5 lb.

Who Can Recomp?

Losing fat and gaining muscle at the same time is most realistic for beginners to resistance training, people returning after a break, and those with more body fat to lose. Experienced, lean lifters usually find it slow, and often do better alternating between focused fat-loss and muscle-gain phases. Whoever you are, recomposition needs three things: progressive resistance training, enough protein (commonly 1.6 to 2.2 g per kg of bodyweight a day), and a small calorie deficit or roughly maintenance calories.

Tracking a Recomp

Because fat and muscle change together, weight alone can stall for weeks while your body improves. Track several signals: waist and hip measurements, progress photos in the same light, the weights you lift, and body fat measured the same way each time. If your waist is shrinking and your lifts are rising, the recomp is working, whatever the scale says. Weekly averages of daily weigh-ins are far more useful than single readings.

How Accurate Are Body Fat Readings?

Bioimpedance scales, skinfold callipers and tape-measure formulas can each be several percentage points out, and readings change with hydration, meals and time of day. A DEXA scan is more accurate but still has error. The goal weight is only as good as the body fat figure you enter, so use the same method under the same conditions and focus on the trend rather than any single number.

Setting a Realistic Target

Typical healthy body fat ranges are very roughly 10 to 20 percent for men and 18 to 28 percent for women, with visible abdominal definition usually appearing around the lower end. Very low body fat levels — under about 8 percent for men or 15 percent for women — are hard to maintain and can affect hormones, energy and mood. A target a few percentage points below where you are now is a good first goal.

Nutrition for a Recomp

Calories and protein do most of the work. A small deficit of about 10 to 20 percent below maintenance lets fat come off while leaving enough energy to train hard and hold on to muscle; beginners with plenty of fat to lose can sometimes recomp at maintenance. Protein is the priority nutrient: aim for about 1.6 to 2.2 g per kg of bodyweight a day, spread across meals, with a good source at each one. Carbohydrate around training helps performance, and enough fat — roughly a quarter to a third of calories for most people — supports hormones and general health. Consistency across weeks matters far more than any single day.

Training for a Recomp

Resistance training is the signal that tells the body to keep and build muscle while fat is lost. Train each major muscle group two or three times a week with compound lifts such as squats, presses, rows and deadlifts, and aim to add a little weight or a rep over time. Cardio helps with the energy deficit and with health, but it should not crowd out recovery from lifting. Sleep of seven to nine hours supports both fat loss and muscle repair, and poor sleep makes appetite harder to control.

Understanding Your Result

The headline is your goal weight at the target body fat percentage.

The now line splits your current weight into fat and lean mass.

The change line shows the fat, lean mass and scale weight changes.

The timeline line gives a rough time to lose the fat at about 0.5 kg a week.

When Should You Use This Calculator?

Use it to set a goal weight based on body composition, not just the scale.

Use it to see how much fat you actually need to lose.

Use it to understand why the scale moves slowly during a recomp.

Common Mistakes

Judging progress by weight alone. Muscle gain hides fat loss on the scale.

Trusting one body fat reading. Track the trend with the same method.

Cutting calories too hard. A large deficit makes keeping muscle harder.

Skipping resistance training. Without it, weight lost includes more muscle.