BMR Calculator
Your BMR is the number of calories your body needs to maintain basic functions at complete rest. Your TDEE adjusts for your activity level to give your total daily calorie needs.
How it works
The Mifflin-St Jeor equation (1990) estimates BMR from weight, height, age, and sex. It is more accurate than the older Harris-Benedict equation (1919) for most healthy adults. TDEE multiplies BMR by an activity factor based on how much you exercise.
Formula
BMR (male) = 10W + 6.25H − 5A + 5; TDEE = BMR × activity factor
BMR estimates the calories your body needs at complete rest. Multiply by an activity factor to get total daily expenditure.
| Symbol | Variable | Unit | Description |
|---|---|---|---|
| W | Weight | kg | |
| H | Height | cm | |
| A | Age | years |
Worked example
70 kg male, 175 cm, 25 years old, moderate exercise
- Weight:
- 70 kg
- Height:
- 175 cm
- Age:
- 25
- Sex:
- Male
- Activity:
- Moderate
BMR = 10×70 + 6.25×175 − 5×25 + 5 = 700 + 1093.75 − 125 + 5 = 1673.75 ≈ 1674 kcal/day. TDEE = 1674 × 1.55 = 2594 kcal/day.
Limitations
Not validated for athletes with unusual body composition, pregnant women, people with metabolic disorders, or children under 18.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is your calorie need at total rest (if you stayed in bed all day). TDEE is your actual daily calorie need, accounting for physical activity. Most people use TDEE for diet planning.
Which equation is most accurate — Mifflin-St Jeor or Harris-Benedict?
Mifflin-St Jeor (1990) is generally more accurate for healthy adults. Harris-Benedict (1919, revised 1984) tends to overestimate BMR slightly. Both are population estimates with ±10–15% individual variation.
Does BMR change as I lose weight?
Yes — BMR decreases as you lose weight because your body needs less energy to maintain a smaller mass. Recalculate your BMR and TDEE as your weight changes.
Can I eat at my BMR to lose weight?
Eating at your BMR (ignoring activity) creates a deficit compared to TDEE and will cause weight loss, but it's usually too severe. Most guidelines recommend a 500–750 kcal/day deficit from TDEE for sustainable fat loss (~0.5 kg/week).
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Last reviewed: 2026-08-22.