Free deficit calculator
Calorie Deficit Calculator — Lose Fat at Your Pace
Fat loss comes down to one thing: a **calorie deficit** — eating less than you burn. The size of that deficit decides how fast you lose, and how sustainable it feels.
This calculator finds your maintenance calories, then sets a daily target for the rate of loss you choose — without dropping into unsafe territory.
Daily calorie target
2,083kcal/day
Daily deficit
−550
Estimated loss
0.50 kg
We won't drop below a safe floor — very low intakes backfire by slowing your metabolism.
How big should your deficit be?
A pound of fat holds roughly 3,500 calories; a kilogram about 7,700. So a 500-calorie daily deficit predicts about 0.5kg (1lb) of loss per week. But faster isn't better — push the deficit too hard and you lose muscle, your energy tanks, and your metabolism adapts down.
- Relaxed (~0.25kg/week) — easiest to sustain, best when you have time
- Standard (~0.5kg/week) — the sweet spot for most people
- Aggressive (~0.75kg/week) — faster, but harder on energy and muscle
Why we cap the deficit
This calculator won't take you below a safe floor (around 1,500 calories for men, 1,200 for women). Eating less than that rarely speeds fat loss — instead it accelerates muscle loss and triggers the metabolic adaptation that makes the last few pounds so stubborn.
Slower, steadier deficits keep more muscle and are far easier to stick to, which is what actually determines whether you reach your goal.
The deficit that adjusts itself
Here's the catch every static calculator misses: as you lose weight, your maintenance calories fall, so a fixed deficit shrinks over time and progress stalls. WhispCal's Autopilot mode watches your real weight trend and nudges your target down as you go — keeping the deficit honest without you recalculating anything.
Frequently asked questions
How many calories should I cut to lose weight?
A deficit of 300–500 calories per day suits most people, producing about 0.3–0.5kg of loss per week. Larger or very active people can sometimes go higher, but bigger isn't automatically better.
Is a 1,200-calorie diet safe?
For many women it's the lowest reasonable floor, and for most men it's too low. Very low intakes are hard to sustain and risk muscle loss. Build your deficit from your maintenance calories rather than chasing a low number.
Why has my weight loss stalled?
Usually because your maintenance calories dropped as you lost weight, erasing your deficit — or because of water retention masking real fat loss. Tracking your weight trend over weeks, not days, and adjusting your target fixes both.
How fast can I safely lose weight?
Around 0.5–1% of your bodyweight per week is a sensible ceiling. Faster than that and you'll lose a meaningful amount of muscle along with the fat.
Keep exploring
Let WhispCal do the math automatically
These numbers are a starting point. WhispCal measures how your body actually responds — logging food in 3 seconds by voice, photo, or barcode — and auto-adjusts your targets as your metabolism changes. Free on iOS and Android.
Free on iOS & Android