Body Recomposition Calculator

About Body Recomposition Calculator

The Body Recomposition Calculator solves a question every lifter eventually asks: can I lose fat and gain muscle at the same time, and if so, how should I eat? Most calculators give a single calorie target and a generic macro split, treating recomposition as either a small cut or a small bulk. That's not how it actually works in practice. This calculator is built around three ideas the others miss: a feasibility score that tells you whether recomp is realistic for you in the first place, a calorie-cycling schedule that respects how training and rest days demand different fueling, and projections that scale with your training experience using a published muscle-gain model.

What makes this calculator different

How to use the Body Recomposition Calculator

1. Pick a quick example (novice male, beginner female, returning lifter, or intermediate) to populate every field with a realistic scenario, or enter your own numbers from scratch.
2. Toggle the unit system at the top — imperial for pounds and inches, metric for kilograms and centimeters.
3. Enter your sex, age, weight, height, and body fat percentage. If you don't know your body fat, leave the field blank and the calculator will estimate it from your BMI using the Deurenberg equation.
4. Pick the activity level that best matches your weekly movement (TDEE multiplier) and your training experience (drives both the feasibility score and the muscle-gain projection rate).
5. Hit "Calculate." Read the Recomp Feasibility Score and verdict, follow the calorie-cycling weekly schedule, hit the macro targets every day, and use the projection table to set 12 / 24 / 52 week expectations.

The math under the hood

Resting metabolic rate uses the Mifflin-St Jeor formula:

\( \text{BMR} = 10 \cdot \text{kg} + 6.25 \cdot \text{cm} - 5 \cdot \text{age} + s \)

where \( s = +5 \) for men and \( s = -161 \) for women. TDEE multiplies BMR by an activity factor between 1.2 (sedentary) and 1.9 (very active).

Lean body mass:

\( \text{LBM} = \text{Weight} \cdot (1 - \text{BF\%}/100) \)

If body fat is unknown, it is estimated using the Deurenberg BMI-based equation:

\( \text{BF\%} \approx 1.20 \cdot \text{BMI} + 0.23 \cdot \text{age} - 10.8 \cdot \text{sex} - 5.4 \)

where \( \text{sex} = 1 \) for men and \( 0 \) for women.

Fat loss projection assumes 7,700 kcal per kilogram of fat tissue. Muscle gain projection uses Lyle McDonald monthly rates by training year, scaled by a 0.70 recomp factor and capped at 5% of starting body weight per year.

Who should run a recomp vs a dedicated cut or bulk

Frequently Asked Questions

Is body recomposition really possible?

Yes, but it is most realistic for novices, returning lifters, people with higher body fat, and those entering or restarting a structured training program. Advanced lifters in lean shape will find pure cut or pure bulk phases far more productive than recomp.

Why does this calculator use calorie cycling instead of a flat number?

On lifting days the body is primed for muscle protein synthesis and benefits from a small surplus. On rest days a deficit drives fat loss without compromising recovery. A flat daily target compromises both goals; cycling lets each day do its job. The weekly average still lands in a small overall deficit.

How is the Recomp Feasibility Score calculated?

The score adds three components. Training experience contributes up to 35 points (novices score highest because of newbie gains). Body fat contributes up to 30 points (mid-range body fat is ideal). Age contributes up to 30 points (younger lifters recover faster). Above 75 you are an excellent candidate; below 35 a dedicated cut or bulk will produce faster results.

How fast should I expect to lose fat and gain muscle?

On a small deficit, expect roughly 0.25 to 0.5 lb (0.1 to 0.25 kg) of fat loss per week. Muscle gain depends entirely on training experience: novices can add 1 to 1.5 lb per month, intermediates 0.5 lb per month, and advanced lifters less than 0.25 lb per month. We scale these rates by 70% to reflect the slower pace of recomp versus a dedicated bulk.

Do I need to track my body fat percentage?

It helps. Body fat anchors your protein target and feasibility score. If you don't have a reliable measurement, leave the field blank and the calculator will estimate it using the Deurenberg BMI-based formula. Track your weight every morning under the same conditions and your waist circumference weekly to verify recomposition is happening even if scale weight stays flat.

Why is protein anchored to lean body mass?

Protein needs scale with the amount of muscle you are protecting and building, not with stored fat. Anchoring protein to lean body mass at 1.0 g per pound (about 2.2 g per kg) gives the right target whether you are lean or carrying extra body fat, and avoids overfeeding protein based on fat mass that does not need it.

Should I follow this exact 4-day training schedule?

The 4-train, 3-rest schedule is a typical recomp split, but the cycling logic works for any number of training days you actually do. If you train 3 days per week, apply the training-day calories on those 3 days and rest-day calories on the other 4 — the weekly average will simply shift slightly.

How long should a recomp phase last?

Plan for at least 12 weeks before evaluating progress. Most lifters need 24 weeks to see clear mirror changes from recomp because both rates (fat loss and muscle gain) are slow when run at the same time. After 24 weeks, reassess: if progress has stalled, switch to a dedicated cut or lean bulk for the next 12 weeks.