Calorie calculator

Estimate how many calories a day keep your weight steady, and how many would lose or gain weight at a gradual pace. It won't suggest going under common safety minimums.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Have a calorie target? Split it into protein, carbs and fat with the macro calculator.

How it's calculated

Maintenance = Mifflin–St Jeor BMR × activity factor
Daily change = weekly rate × 3,500 kcal per lb ÷ 7 (or × 7,700 kcal per kg ÷ 7)
Target = maintenance − daily change (to lose) or + daily change (to gain)

So 1 lb a week is about 500 kcal a day, and 0.5 kg a week is about 550 kcal a day.

Worked example

A 30-year-old man, 180 cm, 80 kg and moderately active, has a maintenance estimate of 1,780 × 1.55 = 2,759 kcal. To lose 0.5 kg a week:

2,759 − 0.5 × 7,700 ÷ 7 = 2,759 − 550 = 2,209 kcal a day

Safety limits

Pace. The CDC and the NHLBI describe a gradual loss of about 1 to 2 lb (roughly 0.45 to 0.9 kg) a week. Faster rates aren't offered here.
Minimum calories. The NHLBI's adult obesity guidelines describe low-calorie diets of 1,000–1,200 kcal a day for women and 1,200–1,500 for men. Calcist uses 1,200 and 1,500 as floors and won't suggest a target below them. If a rate would need fewer calories, you see the floor and a slower expected pace instead.
Going lower than that is something to do only with a doctor's supervision.

Why 3,500 calories per pound is only an approximation

The 3,500 kcal per lb (about 7,700 kcal per kg) rule is a rough figure for the energy in body fat. In practice, weight loss slows over time as your body gets smaller and adapts. The NIH's Body Weight Planner models this more realistically, so use it for longer-term plans.

Limitations

Calorie estimates can be off by 10% or more for an individual. Adjust based on what actually happens over a few weeks.
Not for pregnancy, breastfeeding, children or teens, or anyone with a medical condition affecting weight or eating. A registered dietitian can make a plan for you.

For anyone under 18, these calculators show a pointer to the CDC's BMI-for-age calculator and growth charts instead of adult results, because children and teens are still growing.

Sources

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247.
NHLBI: Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults (1998) — calorie levels for women and men, and the 1–2 lb per week rate.
CDC: Losing weight — gradual loss of about 1–2 lb a week.
NIDDK (NIH): Body Weight Planner
Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837.

Learn: How many calories should I eat a day? · BMR, RMR and TDEE explained

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

Man, 30, 180 cm, 80 kg, moderate, lose 0.5 kg/week: 2,209 kcal ✓
Same man, gain 0.25 kg/week: 3,034 kcal ✓
Woman, 40, 5 ft 5 in, 150 lb, sedentary, lose 1 lb/week: under the 1,200 floor ✓
Same woman, maintain: 1,622 kcal ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

How many calories should I eat to lose weight?

A common approach is about 500 kcal a day below maintenance for roughly 1 lb a week, without going under about 1,200 kcal (women) or 1,500 kcal (men) unless a doctor supervises.

How many calories are in a pound of fat?

The usual figure is 3,500 kcal per pound, or about 7,700 per kilogram. It's an approximation, and real weight loss slows over time.

Why am I not losing weight at the predicted rate?

Water shifts, estimate error and the body adapting all play a part. Track for 2–4 weeks before adjusting.

How many calories do I need to gain weight?

A small surplus of about 250–500 kcal a day gives a gradual gain of roughly 0.25–0.5 kg (0.5–1 lb) a week.

Related calculators

TDEE calculatorTotal daily energy expenditure at every activity level.Macro calculatorProtein, carb and fat grams from a calorie target.BMR calculatorCalories burned at rest: Mifflin–St Jeor, Harris–Benedict, Katch–McArdle.Protein calculatorDaily protein from the RDA and sports nutrition ranges.