How to use
- Choose Metric or Imperial and enter your sex, age, weight and height.
- Pick the activity level that matches a typical week.
- Choose a goal: maintain, or lose or gain a set amount each week.
- Read your daily target in kcal and kJ, and compare every goal in the table.
How it works
First we estimate your resting burn with the Mifflin-St Jeor equation (1990):
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Then TDEE = BMR × activity factor. The factors are the National Academies’ 2023 example values:
| Activity level | Factor | A typical day |
|---|---|---|
| Inactive | 1.4 | Everyday tasks only |
| Low active | 1.6 | Plus about an hour of brisk walking |
| Active | 1.75 | Walking plus about 1½ hours of moderate exercise |
| Very active | 2.05 | About 2 hours of exercise, some vigorous |
For goals we use the common rule of about 7,700 kcal per kg (3,500 kcal per lb) of body weight.
| Weekly change | Daily change |
|---|---|
| 0.25 kg (0.5 lb) | 275 kcal (250 kcal) |
| 0.5 kg (1 lb) | 550 kcal (500 kcal) |
| 0.75 kg (1.5 lb) | 825 kcal (750 kcal) |
Examples
- Man, 25, 180 cm, 80 kg, inactive: BMR 1,805 kcal, so maintenance is 1,805 × 1.4 = 2,527 kcal (10,573 kJ). To lose 0.5 kg a week: 1,977 kcal.
- Woman, 30, 165 cm, 60 kg, inactive: maintenance 1,848 kcal. Losing 0.75 kg a week would mean 1,023 kcal, so we show the 1,200 kcal minimum instead: about 0.59 kg a week.
Safe minimums
We never suggest less than 1,200 kcal a day for women or 1,500 for men. Going lower is only advised under a health professional’s supervision (Harvard Health). The NHS suggests losing 0.5 to 1 kg (1 to 2 lb) a week.
Why our activity factors are higher than some calculators
Many calculators use 1.2 for “sedentary”. We couldn’t trace that number to a primary source. The National Academies’ factors come from studies that measured real energy use, and their lowest category is about 1.4.
The 7,700 kcal rule is a simplification. As you lose weight you burn less, so real loss slows over time. The NIH Body Weight Planner models this.
Want the formula detail? The BMR calculator compares Mifflin-St Jeor with Harris-Benedict and Katch-McArdle.