worldofcalcsBMR Calculator
What is BMR?
Your basal metabolic rate (BMR) is the energy your body uses at complete rest just to stay alive: breathing, circulation, keeping warm and repairing cells. For most people it is 60–70% of the calories they burn in a day. BMR is the starting point for working out how much to eat; your activity is added on top to give your total daily needs.
Mifflin-St Jeor equation
This equation, published in 1990, is the one dietitians most often use because it predicts measured BMR better than the older Harris-Benedict formula. It gives calories (kcal) per day. It doesn't know your muscle mass, so very muscular people burn somewhat more than it predicts.
Good to know
- BMR falls by roughly 1–2% per decade after your 20s, mostly because muscle mass declines; strength training slows this.
- Eating far below your BMR for long periods can slow your metabolism and cost muscle; most diets should stay above it.
- Muscle burns more energy at rest than fat, so two people of the same weight can have different BMRs.
- BMR is not the calories you should eat. Multiply it by your activity level (see the calorie calculator) to get your daily needs.
- These are estimates for healthy adults. Speak to a doctor or dietitian if you are pregnant, have a medical condition or plan a big change in diet.
Worked example
- A 30-year-old man weighing 70 kg and 170 cm tall
- BMR = 10 × 70 + 6.25 × 170 − 5 × 30 + 5 = 700 + 1,062.5 − 150 + 5 = 1,617.5, about 1,618 kcal a day
- A 30-year-old woman weighing 60 kg and 160 cm tall: 600 + 1,000 − 150 − 161 = 1,289 kcal a day
- With moderate exercise (×1.55), the man needs about 2,507 kcal a day to keep his weight
BMR and daily needs at each activity level
For a 30-year-old man (70 kg, 170 cm) and woman (60 kg, 160 cm).
| Activity level | Multiplier | Man (kcal a day) | Woman (kcal a day) |
|---|---|---|---|
| BMR only (at rest) | — | 1,618 | 1,289 |
| Sedentary (little exercise) | ×1.2 | 1,941 | 1,547 |
| Light (1–3 days a week) | ×1.375 | 2,224 | 1,772 |
| Moderate (3–5 days a week) | ×1.55 | 2,507 | 1,998 |
| Active (6–7 days a week) | ×1.725 | 2,790 | 2,224 |
| Very active (physical job or twice a day) | ×1.9 | 3,073 | 2,449 |
The first row is BMR alone; the others are total daily energy needs (TDEE).