How big should my calorie deficit be?

A deficit of 250–1,000 kcal a day (about 10–25% of maintenance) loses 0.5–2 lb a week for most adults. Larger deficits are harder to sustain and cost more muscle.

How many calories should I eat to lose 1 lb a week?

About 500 kcal below your maintenance. For a moderately active 35-year-old man at 5 ft 10 in and 180 lb, that is about 2,224 kcal/day.

Is the 3,500 calorie rule exact?

No. It is a reasonable average for planning, but early loss includes water and later loss slows as maintenance falls. Use the timeline as a guide.

What is the lowest calorie intake that is safe?

Without medical supervision, common guidance is no lower than about 1,200 kcal/day for women and 1,500 for men.

Why am I not losing weight in a deficit?

Intake is often underestimated and activity overestimated. Weigh and log food for two weeks, use a lower activity level, and compare your weekly average weight.

Calculators · Browser · Free

Calorie Deficit Calculator

A calorie deficit means eating fewer calories than you burn. Enter your current and goal weight and how fast you want to lose, and the calculator gives a daily calorie target and a realistic timeline.

How the deficit is calculated

Maintenance calories come from the Mifflin-St Jeor BMR multiplied by your activity factor. A pound of fat is treated as about 3,500 kcal (7,700 kcal per kg), so losing 1 lb a week needs a deficit of 3,500 ÷ 7 = 500 kcal a day.

Example: a 35-year-old man, 5 ft 10 in and 180 lb, moderately active, maintains on 2,724 kcal/day. To reach 165 lb at 1 lb a week he eats about 2,224 kcal/day and gets there in about 15 weeks.

Choosing a safe pace

Most guidelines suggest 0.5–2 lb (0.25–1 kg) a week. Faster loss usually means more muscle lost and a diet that is harder to keep. The calculator warns when the target drops under 1,200 kcal/day for women or 1,500 for men, levels generally not advised without medical supervision.

As you lose weight your maintenance falls, so the same intake produces a smaller deficit over time. The result shows your maintenance at the goal weight so you can plan the step down.

These are estimates for healthy adults, not medical advice. If you are pregnant or breastfeeding, under 18, or managing a medical condition or an eating disorder, ask a doctor or registered dietitian before changing how much you eat.

From 180 lb to 165 lb — 35-year-old man, 5 ft 10 in, moderately active
Weekly loss	Daily deficit	Daily calories	Time to goal
0.5 lb	250 kcal	2,474 kcal	30 weeks (6.9 months)
1 lb	500 kcal	2,224 kcal	15 weeks (3.5 months)
1.5 lb	750 kcal	1,974 kcal	10 weeks (2.3 months)
2 lb	1,000 kcal	1,724 kcal	8 weeks (1.7 months)

Frequently asked questions

How big should my calorie deficit be?: A deficit of 250–1,000 kcal a day (about 10–25% of maintenance) loses 0.5–2 lb a week for most adults. Larger deficits are harder to sustain and cost more muscle.
How many calories should I eat to lose 1 lb a week?: About 500 kcal below your maintenance. For a moderately active 35-year-old man at 5 ft 10 in and 180 lb, that is about 2,224 kcal/day.
Is the 3,500 calorie rule exact?: No. It is a reasonable average for planning, but early loss includes water and later loss slows as maintenance falls. Use the timeline as a guide.
What is the lowest calorie intake that is safe?: Without medical supervision, common guidance is no lower than about 1,200 kcal/day for women and 1,500 for men.
Why am I not losing weight in a deficit?: Intake is often underestimated and activity overestimated. Weigh and log food for two weeks, use a lower activity level, and compare your weekly average weight.