How it works
Basal metabolic rate is the energy your body uses doing nothing at all — breathing, pumping blood, keeping warm. This calculator uses the Mifflin–St Jeor equation, the most accurate of the common formulas for healthy adults:
- Men: BMR = 10 × kg + 6.25 × cm − 5 × age + 5
- Women: BMR = 10 × kg + 6.25 × cm − 5 × age − 161
- Enter sex, age, height and weight.
- The formula returns calories per day at complete rest.
- Multiply by an activity factor to get what you actually burn in a day.
| Activity level | Multiplier |
|---|---|
| Sedentary — desk job, little exercise | 1.2 |
| Light — exercise 1–3 days a week | 1.375 |
| Moderate — exercise 3–5 days a week | 1.55 |
| Very active — exercise 6–7 days a week | 1.725 |
| Extra active — hard training or physical job | 1.9 |
That multiplication is exactly what the calorie calculator does when it shows maintenance calories.
Examples
Worked examples, straight from the equation:
- Man, 30, 175 cm, 75 kg: 10×75 + 6.25×175 − 5×30 + 5 = 1699 kcal/day. Moderately active (×1.55) that is about 2633 kcal.
- Woman, 30, 163 cm, 62 kg: 10×62 + 6.25×163 − 5×30 − 161 = 1328 kcal/day, or about 1826 kcal when lightly active.
BMR falls roughly 5 kcal per year of age and rises about 10 kcal for every extra kilogram of body weight.
These formulas are population averages published in peer-reviewed research. They cannot see your muscle mass, frame or medical history, so treat the result as a starting point and talk to a doctor or dietitian before making big changes.
BMR Calculator: frequently asked questions
- What is BMR?
- Basal metabolic rate: the calories your body uses at complete rest to breathe, circulate blood and keep organs working. It is typically 60–70% of daily energy use.
- How do I get my daily calorie needs from BMR?
- Multiply BMR by an activity factor: 1.2 (sedentary) to 1.9 (very active). The table in the calculator does this for you.
- Mifflin–St Jeor or Harris–Benedict?
- Studies find Mifflin–St Jeor the more accurate for most adults, so it is the main result; revised Harris–Benedict is shown for comparison.