Free tool
Free Calorie Deficit Calculator
See what a gentle, standard or aggressive calorie deficit looks like for your body — and roughly how fast each one moves the scale.
Everything runs in your browser. No account, no data stored.
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Please note: These calculators give general estimates from population-level formulas. They are not medical advice, and they may not reflect people on GLP-1 medications precisely — appetite suppression, rapid weight loss, and lean-mass changes all shift the real numbers. Always consult your prescriber for personalized guidance.
How the deficit is calculated
First we estimate your TDEE (Mifflin-St Jeor BMR × activity factor), then subtract 10%, 20% or 25%. Roughly 7,700 kcal equals one kilogram of body mass, which is where the weekly projection comes from.
A 20% deficit is the usual sweet spot: fast enough to see progress, slow enough to hold onto muscle. We flag any option that drops below 1200 kcal (women) or 1500 kcal (men), because very low intakes make adequate protein and micronutrients almost impossible.
Deficits and muscle on a GLP-1
GLP-1 medications often create a much deeper deficit than intended, because appetite falls faster than your plan does. The scale drops quickly — and a large share of that can be lean tissue.
The protective combination is simple and non-negotiable: keep the deficit moderate, hit your protein target every day, and lift something heavy two or three times a week.