Calorie Deficit Calculator — daily target for weight loss

This is an estimate, not medical or dietary advice. Calorie needs vary with body composition, medications and health. Very low intakes can be unsafe: the NHLBI clinical guidelines describe a low-calorie diet as roughly 1,000–1,200 kcal/day for women and 1,200–1,500 kcal/day for men, and say diets below 800 kcal/day are not recommended without medical supervision. Talk to a doctor or dietitian before a big change, especially if you are pregnant, under 18, or managing a health condition.

How it works

Two steps: find how much you burn, then eat less than that.

• Maintenance calories (TDEE) = your BMR (resting burn) from the Mifflin-St Jeor equation, multiplied by an activity factor (PAL) from the FAO/WHO published levels. This is what keeps your weight steady.
• Daily target = maintenance − your chosen deficit. Common deficits are ~250/day (gentle), ~500/day (moderate), and ~750–1,000/day (faster, and harder to sustain). The deficit is capped at your maintenance, so the target never drops below zero.

Why no "pounds per week" figure? The popular "3,500 calories = 1 pound" shortcut assumes a straight line, but as you lose weight you burn fewer calories, so real loss slows and falls short of that estimate — it systematically over-promises. This calculator gives you the daily intake target and stops there; recompute your maintenance as your weight changes, and track real progress on the scale over weeks.

Watch the floor. If your target lands below the NHLBI figures above (~1,200 kcal for women, ~1,500 for men), that is a very aggressive deficit — ease it or get medical guidance rather than pushing intake down further.

Worked example

A 30-year-old man, 178 cm, 82 kg, desk job (sedentary):

• BMR (Mifflin-St Jeor): 10×82 + 6.25×178 − 5×30 + 5 = 1,787.5 kcal
• Maintenance: 1,787.5 × 1.53 (sedentary PAL) ≈ 2,735 kcal/day
• With a 500-calorie deficit → daily target ≈ 2,235 kcal/day

Frequently asked questions

How big a calorie deficit is safe?

A deficit of about 500 calories a day is a common, sustainable starting point. Larger deficits cut calories faster but are harder to keep up and risk losing muscle. Keep your target above the NHLBI low-calorie range (roughly 1,200 kcal for women, 1,500 for men) unless a clinician is supervising you; diets under 800 kcal/day are not recommended on your own.

Should I create the deficit by eating less or exercising more?

Either works, and both together is common. Eating less is usually the larger lever; exercise adds to the deficit, helps preserve muscle, and has health benefits beyond weight. This calculator counts activity in your maintenance figure, so don't also subtract exercise calories or you'll double-count.

What are maintenance calories (TDEE)?

The total calories you burn in a day at your current weight and activity — resting metabolism plus everything you do. Eat that amount and your weight holds steady; eat less and you lose, more and you gain. As you lose weight this number falls, so recalculate it periodically.

Why doesn't it tell me how many pounds I'll lose?

Because a simple calories-to-pounds conversion over-promises. Real loss depends on what tissue you lose and how your metabolism adapts as you get lighter, so a straight-line weekly figure tends to overstate results over months. The honest answer is a daily target plus real tracking, which is what this tool gives you.

Does this work for building muscle or a "bulk"?

This calculator is for a deficit. To gain, you'd eat above maintenance (a surplus) rather than below it. Pair either goal with adequate protein — see the macro and protein calculators.

Is a calorie deficit safe for everyone?

No. If you are pregnant or breastfeeding, under 18, have a history of disordered eating, or manage a condition such as diabetes, don't cut calories without medical guidance — whether to diet at all, and how, is a clinical decision. For everyone else, a gentler deficit you can sustain beats an aggressive one you can't, and staying above the safe-calorie floor matters more than losing quickly.