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Calorie calculator
Find out roughly how many calories you burn in a day and how many to eat to lose, keep or gain weight. The calculator starts from your basal metabolic rate, multiplies it by your activity level and adds or removes a daily amount for your goal. Every number is an estimate, and this page explains how far you can trust it.
This calculator gives estimates for healthy adults and is not medical or nutritional advice. It is not suitable during pregnancy or breastfeeding, for people under 18 or for those with eating disorders or medical conditions. Before a weight-loss diet, especially a strict one, talk to a doctor or a registered dietitian.
How to use it
- Enter your details. Choose sex, then type age, weight and height. US units are the default; switch to metric if you prefer kilograms and centimeters.
- Pick activity and goal. Choose the activity level that matches a normal week, not your best one, and the pace you want: maintain, lose or gain 0.5 to 2 lb a week.
- Read the target. You get your daily calories for the goal, your BMR, your maintenance calories and the rough change after four weeks. If the target falls below the usual minimum, a warning appears.
How the estimate is built
Step 1: basal metabolic rate (BMR). This is the energy your body uses at complete rest. By default the calculator uses the Mifflin-St Jeor equation, published in 1990 from measurements on 498 adults aged 19 to 78: 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women. A 2005 systematic review found it the most reliable of the common equations: it came within 10% of measured values for more people than the others, though individual errors can still be larger.
Step 2: total daily energy expenditure (TDEE). BMR is multiplied by an activity factor, from 1.2 for a desk job with little exercise to 1.9 for hard physical work or training twice a day. The result is your maintenance level: the calories that keep your weight stable.
Step 3: the goal. To lose weight the calculator removes a daily amount from maintenance; to gain, it adds one. It uses the classic rule of about 3,500 kcal per pound (7,700 kcal per kg): losing 1 lb a week means about 500 kcal less a day.
Activity levels and their limits
| Level | Typical week | Factor |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Exercise 1–3 days a week | 1.375 |
| Moderately active | Exercise 3–5 days a week | 1.55 |
| Very active | Hard exercise 6–7 days a week | 1.725 |
| Extra active | Physical job or training twice a day | 1.9 |
These multipliers are a widely used convention, usually attributed to exercise physiology textbooks such as McArdle, Katch and Katch; we could not trace their original study, so treat them as an approximate convention. For comparison, the FAO/WHO/UNU report on human energy requirements (2004) groups lifestyles by physical activity level: 1.40 to 1.69 for sedentary or light, 1.70 to 1.99 for active and 2.00 to 2.40 for vigorous. Most people overestimate their activity: if you are unsure, choose the lower level and adjust after a few weeks.
Worked examples
Woman, 35, 150 lb, 5 ft 6 in, lightly active, lose 1 lb a week
BMR 1,390 kcal × 1.375 = maintenance of about 1,910 kcal. Removing 500 kcal a day gives a target of 1,420 kcal a day, above the 1,200 kcal minimum.
Man, 40, 190 lb, 5 ft 10 in, moderately active, lose 1 lb a week
BMR 1,780 kcal × 1.55 = maintenance of about 2,760 kcal. The target is 2,260 kcal a day. With Katch-McArdle and 20% body fat the BMR would be 1,860 kcal and maintenance 2,880 kcal: the two equations rarely agree exactly.
When the target is too low
A sedentary woman of 50, 132 lb and 5 ft 3 in has a maintenance of about 1,430 kcal. Asking for 2 lb a week would mean only 430 kcal a day, far below 1,200: the calculator shows a warning. A slower pace is the realistic option.
How accurate is it?
Equations predict an average person with your size, age and sex. Your real metabolism can differ by a few hundred calories because of muscle mass, genetics, health conditions and medication. Use the result as a starting point, track your weight for three or four weeks and adjust by 100 to 200 kcal if needed.
The 3,500 kcal per pound rule also has limits. As Kevin Hall of the NIH showed, it overestimates long-term weight loss, because the body burns less as it gets lighter and part of the early loss is water. Expect progress to slow after the first weeks: that is normal, not failure.
Katch-McArdle (370 + 21.6 × lean body mass in kg) ignores sex and age and relies only on lean mass, so it can be better for very lean or very muscular people, but only if your body fat percentage is reliable. Its original publication could not be verified; it is reported in exercise physiology textbooks.
To see whether your weight is in the healthy range for your height, use the BMI calculator. To work out a percentage change, such as how much 500 kcal is of your maintenance, the percentage calculator does it instantly.
Sources
- Mifflin MD, St Jeor ST et al., "A new predictive equation for resting energy expenditure in healthy individuals", American Journal of Clinical Nutrition 1990;51(2):241-247.
- Frankenfield D, Roth-Yousey L, Compher C, "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review", Journal of the American Dietetic Association 2005;105(5):775-789.
- Katch-McArdle equation (370 + 21.6 × lean body mass): reported in McArdle, Katch and Katch, Exercise Physiology; original publication not verified.
- Activity factors 1.2 to 1.9: approximate convention attributed to the same textbooks; FAO/WHO/UNU, Human energy requirements (2004), physical activity levels.
- Hall KD, "What is the required energy deficit per unit weight loss?", International Journal of Obesity 2008;32:573-576; Hall KD et al., The Lancet 2011;378:826-837.
- Harvard Health Publishing, "Calorie counting made easy" (2024): intake should not go below 1,200 kcal for women or 1,500 kcal for men without medical supervision.
Sources checked on October 14, 2026.
Frequently asked questions
How many calories should I eat to lose weight?
What is the difference between BMR and TDEE?
Which equation should I choose?
Why is there a minimum of 1,200 or 1,500 calories?
Why did my weight loss slow down?
Should I eat back the calories I burn exercising?
Can I use this calculator if I am pregnant or under 18?
Last updated Wednesday, October 14, 2026