Calorie Calculator
The Mifflin-St Jeor equation gives a 30-year-old man who is 180 cm and 80 kg a basal metabolic rate of 1780 kcal a day. With moderate exercise (x 1.55) he needs about 2,759 kcal a day to maintain his weight.
How to use
- Choose your sex and enter age, height and weight. Switch to US units for feet, inches and pounds.
- Pick the activity level that matches a typical week.
- Pick a goal: maintain, or lose or gain weight at a moderate or faster pace.
- Read your estimated maintenance calories (TDEE) and the daily target for your goal.
How it works
Basal metabolic rate (BMR) uses the Mifflin-St Jeor equation: 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years), then + 5 for men or - 161 for women. A 30-year-old man at 80 kg and 180 cm has 800 + 1,125 - 150 + 5 = 1,780 kcal.
Total daily energy expenditure (TDEE) is BMR times an activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 active, 1.9 very active.
For weight change, about 3,500 kcal is treated as 1 lb (0.45 kg) of body weight. A deficit or surplus of 500 kcal a day is roughly 1 lb a week, and 1,000 kcal roughly 2 lb. This is a rough rule: the body adapts, so real change slows over time.
The result is an estimate for healthy adults aged 15 to 100 and can be off by 10 percent or more. Intakes below 1,200 kcal (women) or 1,500 kcal (men) a day are generally not advised without medical supervision, and this tool flags targets under those levels. This is not medical advice. Talk to a doctor or dietitian before changing your diet, especially if you are pregnant, breastfeeding, under 18, or have a medical condition.
Activity factors
| Level | Factor | Typical week |
|---|---|---|
| Sedentary | 1.2 | Little or no exercise, desk job |
| Light | 1.375 | Light exercise 1 to 3 days |
| Moderate | 1.55 | Moderate exercise 3 to 5 days |
| Active | 1.725 | Hard exercise 6 to 7 days |
| Very active | 1.9 | Hard exercise plus a physical job |
Sources and disclaimer
Equation: Mifflin MD, St Jeor ST et al., "A new predictive equation for resting energy expenditure in healthy individuals", American Journal of Clinical Nutrition 51(2), 1990. Evaluation: Frankenfield D et al., Journal of the American Dietetic Association 105(5), 2005. Activity multipliers follow the common Harris-Benedict convention. 1,200 and 1,500 kcal minimums follow general guidance from Harvard Health and the NIH.
This tool is not medical advice. See a doctor or registered dietitian for personal guidance.
Sources: Mifflin-St Jeor (AJCN 1990) · Frankenfield (JADA 2005)Last reviewed 2026-10-13
FAQ
How many calories should I eat to lose weight?
Subtract from your maintenance calories (TDEE). A deficit of about 500 kcal a day is a common starting point. Keep the target above the minimums of 1,200 (women) or 1,500 (men) kcal unless a doctor supervises.
Why Mifflin-St Jeor?
In a 2005 review the American Dietetic Association found it the most reliable of the common equations for estimating resting energy in healthy adults, though it can still be off for individuals.
Does it work for athletes or very muscular people?
It does not use body composition, so it tends to underestimate needs for very lean, muscular people and overestimate for people with a lot of body fat.
Is my data sent anywhere?
No. The calculation runs in your browser and nothing you enter is sent to a server.