Calorie Deficit Calculator
The daily calories that create a safe deficit for fat loss — with an honest, adaptive timeline instead of a flat 1-lb-a-week promise.
About you
Add it to switch to the lean-mass Katch-McArdle formula.
Activity
Goal & nutrition
Used for your timeline estimate.
Daily calories to lose
−490 cal vs maintenance
BMR (at rest)
Mifflin-St Jeor
TDEE (maintenance)
Burned per day
Daily deficit
vs maintenance
Weekly change
projected loss
Maintenance at each activity level
Most people sit between two of these. If the scale isn't moving, you're likely closer to the lower number.
How it works
We find your maintenance calories (TDEE), then subtract your chosen deficit to get a daily target for fat loss. About 7,700 calories equals a kilogram of body fat (3,500 per pound), so a 500-calorie daily deficit starts at roughly 0.5 kg / 1 lb per week — but only at first. The Timeline recomputes your burn as you lose, so you can see the loss decelerate and find where to recalculate.
Deficit target
target = TDEE − deficit; weekly loss ≈ (deficit × 7) / 7700 kg
- TDEE
- maintenance calories
- deficit
- 15–25% of TDEE (≈300–600 cal) recommended
- 7700
- calories per kg of body mass (3,500 per lb)
Worked example
- TDEE = 2,530 cal/day
- Deficit = 20% (506 cal)
- Target = 2,530 − 506
- Weekly loss ≈ (506 × 7) / 7700
≈ 2,024 cal/day, about 0.46 kg (1 lb) of fat loss in week one.
Good to know
- The “3,500 calories = 1 lb” rule is true once, not forever — your deficit shrinks as you get lighter, which is the whole point of the adaptive Timeline.
- Never eat below the safety floor (1,500 cal men / 1,200 women) without medical guidance; the calculator enforces it.
- Weight fluctuates daily from water and food in transit. Judge progress on the 7-day average trend, not the morning scale.
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Frequently Asked Questions
What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns (your TDEE), so it makes up the difference from stored fat. It is the one requirement for fat loss — every diet works by creating a deficit, whatever its name.
How big should my deficit be?
A moderate deficit of 15–25% below maintenance (often 300–600 calories) is the sweet spot: fast enough to see progress, gentle enough to protect muscle and stay consistent. Larger deficits lose more muscle and are harder to sustain.
Why is losing 2 lb every week so hard to keep up?
Because your metabolism adapts. As you get lighter you burn less, so a deficit that started at 500 calories shrinks toward zero. The Timeline tab simulates this and shows the point where your loss stalls and you need to step calories down again.
How do I avoid losing muscle in a deficit?
Keep protein high (2.0–2.4 g/kg), do resistance training, and avoid extreme deficits. The macro split here defaults to higher protein during fat loss for exactly this reason.
What if I stop losing weight?
First check your tracking is honest for two weeks. If you have genuinely plateaued, recalculate at your new weight and take another small step down in calories, or add activity — do not crash your intake.