Calorie Deficit Calculator
The exact daily calorie target for your chosen rate of weight loss — and how long it'll take.
How a calorie deficit is calculated
One pound of body fat stores roughly 3,500 calories of usable energy. To lose a pound of fat in a week, you need a weekly deficit of ~3,500 cal — or 500 cal/day. Scale the deficit up or down for faster or slower loss.
The four standard paces
- −250 cal/day (0.5 lb/week) — gentle, for the already-lean.
- −500 cal/day (1 lb/week) — the gold standard.
- −750 cal/day (1.5 lb/week) — for higher body-fat starting points.
- −1,000 cal/day (2 lb/week) — the upper limit. Hard to sustain.
Never drop daily intake below ~1,200 cal (women) or ~1,500 cal (men) without medical supervision — you can't hit micronutrient or protein targets below those levels.
Why progress runs slower than the math
As you lose weight, two things shrink your deficit automatically:
- Less body mass to maintain. A smaller you burns fewer resting calories.
- Adaptive thermogenesis. Your body lowers NEAT (fidgeting, posture, walking) by 100–300 cal/day during restriction.
Recalculate your TDEE every ~10 lb lost and adjust intake to keep the same effective deficit.
Why calculating your deficit is useful
- It replaces willpower with a number. "Eating less" is a feeling. "1,750 cal/day" is a target.
- It sets a realistic timeline. Knowing it'll take 20 weeks to lose 20 lb beats expecting it in 8 and quitting in 6.
- It prevents over-cutting. Too-large deficits drive muscle loss, fatigue, and rebound eating. The math keeps you in the sustainable zone.
- It tells you when the diet is broken. If you've been hitting your target for 3 weeks and the scale hasn't moved, something is wrong — usually tracking accuracy.
- It pairs with protein. A deficit without enough protein burns muscle too. Use the protein calculator to set your floor.
FAQ
What is a calorie deficit?
A calorie deficit is when you consume fewer calories than your body burns. Sustained over time, this forces your body to use stored fat for energy, resulting in weight loss. A deficit of about 3,500 calories produces roughly 1 pound (0.45 kg) of fat loss.
How big should my deficit be?
For most people, 500 cal/day (≈1 lb/week) is the sweet spot. Very lean or older people do better with 200–300 cal. Above 1,000 cal/day risks muscle loss, hormonal disruption, and rebound.
Is the 3,500-calorie rule accurate?
It's a simplification. Expect actual fat loss to be 10–20% slower than the math predicts over multi-month diets, because metabolic adaptation lowers your TDEE as you lose weight.
Why am I not losing weight in a deficit?
The three most common reasons: (1) under-reporting intake by 20–40%, (2) overestimating burn from fitness trackers, and (3) water retention masking fat loss for 2–3 weeks. Track honestly for 14 days before deciding the deficit doesn't work.
Should I take diet breaks?
Yes — 1–2 weeks at maintenance every 6–10 weeks of dieting improves adherence, restores hormones, and doesn't slow long-term fat loss (MATADOR protocol, Byrne et al., 2018).
Sources
- Hall KD. What is the required energy deficit per unit weight loss? Int J Obes. 2008;32(3):573–6.
- Byrne NM, et al. Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes. 2018;42:129–138.