A calorie deficit is eating fewer calories than you burn, so your body taps stored fat and you lose weight. Because roughly 3,500 kcal equals a pound of fat (about 7,700 per kg), a steady daily shortfall sets your pace: 500 kcal/day ≈ 1 lb a week. This calculator turns a target loss rate into the daily deficit and the calories to eat, and flags rates that look too aggressive.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: the 3,500 kcal/lb energy-balance estimate, recomputed in code. General guidance, not medical advice.
The deficit formula
Start from your maintenance calories — your TDEE, the amount that keeps weight steady. Pick a weekly loss, convert it to energy (3,500 kcal per pound or 7,700 per kilogram), and divide by seven for the daily deficit. Subtract that from maintenance to get your target intake. The bigger the deficit the faster the loss, but very large deficits sacrifice muscle and are hard to maintain.
Worked example — TDEE 2500, lose 1 lb/week
Scenario: maintenance 2,500 kcal, goal 1 pound a week.
To lose about 1 pound a week you need a 500 kcal/day deficit, so you'd eat about 2,000 kcal a day — roughly 4.3 lb a month. Wanting 0.5 kg a week instead needs a 550 kcal/day deficit (eat ~1,950). Pushing to 2 lb a week means a 1,000 kcal/day deficit and only 1,500 kcal of food on a 2,500 maintenance — aggressive, and the calculator will say so.
Frequently Asked Questions
Eating fewer calories than you burn, so the body uses stored fat. ~3,500 kcal of deficit ≈ 1 lb lost.
About 500 kcal/day (3,500 ÷ 7). On a 2,500 maintenance, eat ~2,000/day.
Maintenance − deficit. 2,500 − 500 = ~2,000/day. Avoid below ~1,200 (women)/1,500 (men) unsupervised.
About 0.5–1 kg (1–2 lb) a week. 2 lb/week needs a 1,000 kcal/day deficit — aggressive for many.
No — an approximation. Water, muscle and metabolic changes shift real results. Use it for planning.