Tools / Calculator 03
Calorie Deficit Calculator.
Pick a target weekly fat-loss rate. We'll work out the daily calorie target, the weeks to goal, and whether the deficit is sustainable or overshoots clinical floors.
Daily target
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| Maintenance (TDEE) | — |
| Daily deficit | — |
| Weekly fat loss target | — |
| Weeks to goal weight | — |
How it's calculated.
- Energy deficit per pound of fat. Approximately 3,500 kcal. (Multiply by 7,700 for a kilogram.)
- Daily deficit = (target weekly loss × 7,700 kcal/kg) ÷ 7 days.
- Daily target = TDEE − daily deficit.
- Weeks to goal = (current weight − goal weight) ÷ target weekly loss.
Source: Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr, 1958. (Modern caveat: the 3,500 kcal rule overestimates total loss past ~6 weeks because metabolic adaptation kicks in.)
Why aggressive deficits fail.
- Lean mass loss. Deficits over ~25% of TDEE strip muscle alongside fat. The scale moves; the mirror gets worse.
- Adaptive thermogenesis. Metabolism downshifts faster on aggressive deficits — measurable as 100–250 kcal lower TDEE within weeks. Your "small" deficit becomes no deficit.
- Adherence collapses. The literature is consistent: 0.5–0.75% body weight per week is the sweet spot for staying on plan past month two.
- Recovery and sleep. Hard deficits hit cortisol, sleep quality, and lift performance. The compound cost is rarely worth the four extra days saved.
Status flags this calculator uses: In range if the deficit is <25% of TDEE and the daily target stays above 1,200 kcal (women) / 1,500 kcal (men). Watch if the deficit is 25–35%. Aggressive if either threshold is crossed.