How to calculate BMR and TDEE
Knowing your body’s energy needs is the foundation of any diet or training plan. This guide explains what basal metabolic rate (BMR) and total daily energy expenditure (TDEE) mean, and how the calculator works them out with the Mifflin-St Jeor equation and an activity factor. Its worked example sticks to the same values used by Klar’s BMR calculator.
What are BMR and TDEE?
Basal metabolic rate (BMR) is the energy your body burns at complete rest just to stay alive: breathing, heartbeat and organ functions. Total daily energy expenditure (TDEE) adds the effect of your daily activity and is the figure closest to your actual needs. The difference matters: BMR is for rest, TDEE is your full daily need.
The Mifflin-St Jeor equation
The equation computes BMR from weight, height, age and sex: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + (5 for male or −161 for female). The calculator converts units automatically — pounds to kilograms and metres to centimetres — then applies the equation directly.
The activity factor and TDEE
BMR is multiplied by an activity factor matching your routine: 1.2 for sedentary, 1.375 for light activity, 1.55 for moderate, 1.725 for active, and 1.9 for very active. Choosing a realistic level matters: picking higher than your reality inflates TDEE and distorts any diet target built on it.
A worked example
Using the same values as the calculator: male, age 30, weight 80 kg, height 180 cm, moderate activity. BMR = 10×80 + 6.25×180 − 5×30 + 5 = 1,780 calories/day, and TDEE = 1,780 × 1.55 ≈ 2,759 calories/day.
Common mistakes
Among the mistakes: choosing an unrealistic activity level, entering weight in pounds without accounting for the conversion to kilograms, confusing BMR with TDEE, and relying on the figures as medical fact instead of an estimate. The estimates are based on population averages, and your actual needs may differ depending on your body composition and true activity level.
Key takeaways
- BMR is the complete-rest need; TDEE adds the effect of daily activity.
- The equation: 10 × weight + 6.25 × height − 5 × age + sex constant.
- Activity factors range from 1.2 to 1.9 by level.
- A realistic activity level is essential for a sound result.
- Estimates are general and are not medical advice.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is for complete rest, while TDEE adds the effect of your daily activity and is the figure closest to your actual energy needs.
Why does the calculator ask for sex?
Because the Mifflin-St Jeor equation uses a different constant for men and women, reflecting average differences in body composition.
Are the figures accurate for me personally?
They are estimates based on population averages, and your actual needs may differ depending on your body composition and activity level.
Related calculators
BMR calculator
Estimate your basal metabolic rate and daily energy expenditure using the Mifflin-St Jeor equation.
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BMI calculator
Calculate your body mass index from weight and height, and see the healthy weight range for your height.