About Calorie Deficits
Every weight-loss approach that works — low-carb, fasting, meal plans, apps — works through the same mechanism: consuming less energy than you expend. The deficit IS the diet; everything else is a strategy for making the deficit tolerable. That makes this calculator's arithmetic the honest core of the whole industry.
Enter your maintenance calories and pick a loss rate; you get the daily target, the deficit, and safety flags where the math turns aggressive. Don't know your maintenance? Compute it first — the number here is only as good as the TDEE you feed it.
Get your maintenance number from the TDEE Calculator.
The Deficit Math
The convention, stated honestly:
Deficit/day = target rate (lb/week) × 500 Target = TDEE − deficit (1 lb fat ≈ 3,500 kcal — an approximation that ignores water and adaptation)
Worked example: 2,500 maintenance targeting 1 lb/week → eat ~2,000/day (a 3,500 kcal weekly deficit). The same maintenance at 2 lb/week demands 1,500 — doable for some; the calculator warns when the result crosses under ~1,200–1,500, where most people should slow down instead.
Rates and Deficits
The standard rate ladder on a 2,500-kcal maintenance:
| Rate | Daily deficit | Daily target | Monthly loss ≈ |
|---|---|---|---|
| 0.5 lb/week | 250 kcal | 2,250 | ~1 kg / 2.2 lb |
| 1 lb/week | 500 kcal | 2,000 | ~2 kg / 4.3 lb |
| 1.5 lb/week | 750 kcal | 1,750 | ~2.9 kg / 6.5 lb |
| 2 lb/week | 1,000 kcal | 1,500 | ~3.9 kg / 8.7 lb |
The gentle rates look slow until you multiply by a year — 0.5 lb/week is ~26 lb, sustained, without the rebound the steep rates invite.
Why the Scale Won't Cooperate Weekly
The 3,500-kcal rule predicts a straight line; bodies draw a squiggle. Early weeks over-deliver (glycogen and its water leave first), then progress slows below the math as metabolism adapts — a real but modest effect — and daily weight noise (sodium, carbs, hydration, hormones) can swamp a week's true fat loss in either direction. Weigh daily, trend weekly averages, and judge the plan monthly.
Protecting the loss's quality matters as much as its speed: adequate protein and resistance training bias the deficit toward fat rather than muscle, which also defends the metabolism that makes maintenance possible afterwards. And the floor warnings exist for a reason — deficits that crash intake below ~1,200 kcal trade short-term scale wins for nutrient gaps, muscle loss, and the rebound statistics that give dieting its reputation.