🔥 BMR Calculator
Your basal metabolic rate — the calories your body burns at complete rest — from two proven formulas, plus a TDEE table for every activity level.
How to use the BMR Calculator
Enter your age, sex, height and weight to get your basal metabolic rate, then see how that translates into daily calorie needs at different activity levels.
How it works
The Harris-Benedict equation and its modern successor Mifflin-St Jeor estimate the energy your body uses at complete rest. Mifflin-St Jeor is generally preferred because it reflects current body composition better. The formulas differ by several percent, which is why two calculators can give different numbers for the same person.
When to use it
Use it to set a calorie target for cutting or bulking, sanity-check a figure from a fitness tracker, or understand where the numbers in a diet plan came from.
Worked example
For a 30-year-old male, 175 cm, 75 kg:
| Formula | Result |
|---|---|
| Mifflin-St Jeor | 1,737 kcal/day |
| Harris-Benedict (revised) | 1,755 kcal/day |
| Katch-McArdle (needs body fat) | 1,728 kcal/day |
Assumptions and limitations
BMR is a population average, and individual metabolism can deviate by 10 to 15 percent or more. Age, sex, muscle mass, thyroid function, sleep and stress all shift it. It is not valid during pregnancy, for competitive athletes whose energy expenditure differs substantially, or for people under 18. It is not medical advice.
Frequently Asked Questions
What is BMR?
Basal metabolic rate (BMR) is the number of calories your body needs at complete rest to run its basic functions — breathing, blood circulation, cell repair, hormone production and brain activity. For most people it is the largest component of daily energy use, typically 60–70% of total calories burned.
Which BMR formula is more accurate: Mifflin-St Jeor or Harris-Benedict?
The Mifflin-St Jeor equation (1990) is generally considered the most accurate for today's population and is the standard recommendation of the Academy of Nutrition and Dietetics. The revised Harris-Benedict equation (1984) tends to run slightly higher. This calculator shows both so you can treat the result as a small range rather than a single number.
What is the difference between BMR and RMR?
Resting metabolic rate (RMR) is measured under less strict conditions — resting but not after an overnight fast and full sleep — so it is usually slightly higher than BMR. In everyday use the two terms are often treated as interchangeable, and online calculators like this one estimate values in the same range.
Should I eat fewer calories than my BMR?
Generally no, not for long periods. Eating consistently below BMR makes it harder to get enough protein, vitamins and minerals, can accelerate muscle loss and may prompt adaptive thermogenesis — your body reducing its energy expenditure to conserve. For sustainable fat loss, eat between your BMR and your TDEE instead.
Why does BMR decrease with age?
After about age 30, adults lose muscle mass gradually (sarcopenia) unless they do resistance training, and muscle is metabolically expensive tissue. Less muscle means a lower BMR — roughly 1–2% slower per decade after early adulthood. Strength training and adequate protein are the most effective ways to slow this decline.
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