Free tool
Body recomposition calculator
Can you build muscle and lose fat at the same time? This calculator gives you targets and a straight answer. Enter your stats to get a recomp viability read, daily calorie goal, protein target, and a realistic 12-week expectation. Free, no signup, no email gate.
How the math works
TDEE is calculated via the Mifflin-St Jeor equation — the most validated BMR formula for the general population (Mifflin et al., 1990). BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (male) or − 161 (female). TDEE multiplies BMR by an activity factor derived from your weekly training days (1.375 for 1–2 days, 1.55 for 3–4, 1.725 for 5, 1.9 for 6).
The recomp calorie target applies a 12% deficit to TDEE — within the 10–15% range that research identifies as the sweet spot for simultaneous fat loss and muscle-building. Below 10% and the body prioritizes muscle before fat. Above 20% and training quality degrades. Protein is set at 0.9 g/lb (0.8 g/lb if recomp is unlikely) per ISSN guidance (Jäger et al., 2017).
The viability judgment uses training experience and body fat estimate as primary signals. Beginners and returning lifters have a genuine physiological advantage — untrained or re-trained muscle grows faster in response to novel stimulus, even in a deficit. Trained, already-lean individuals face diminishing returns from simultaneous recomp.
What the result is not
These numbers are starting estimates, accurate to roughly ±10%. TDEE calculators estimate — they do not measure. Individual variation in metabolism, training intensity, sleep, and stress all affect real calorie needs. Run the targets for 3–4 weeks, then adjust based on what your mirror, measurements, and strength logs actually show.
No promised numbers for lb of fat lost or muscle gained — those depend on execution, sleep, consistency, and starting point. What is reliable: beginners following high-protein near-maintenance training consistently for 12 weeks will see real changes in body composition and strength.
Related tools and guides
The calculator is the easy part
The numbers take 90 seconds. The hard part is weeks 3 through 12 — reading your weight trend, adjusting protein when life gets busy, keeping training progressive when motivation drops, and knowing what a flat scale actually means for your composition. That is what 1:1 coaching with Kris is for.