BMR Calculator

Estimate your basal metabolic rate with three formulas

Age (years)

Height (cm)

Weight (kg)

I know my body fat %

Your Basal Metabolic Rate

1649

kcal per day

Mifflin-St Jeor

1649

kcal/day

Harris-Benedict

1696

kcal/day

Katch-McArdle

—

needs body fat %

Formulas Used

Mifflin (men): 10 x kg + 6.25 x cm - 5 x age + 5

Mifflin (women): 10 x kg + 6.25 x cm - 5 x age - 161

Katch-McArdle: 370 + 21.6 x lean mass(kg)

Mifflin-St Jeor is the primary estimate. Harris-Benedict is shown for reference, and Katch-McArdle is used when you enter body fat % (it is based on lean body mass).

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What is a BMR Calculator?

A BMR calculator estimates your Basal Metabolic Rate - the energy your body uses at complete rest to keep its vital systems running, such as breathing, circulation, and cell repair. For most people BMR accounts for 60-70% of all calories burned in a day, making it the foundation of any calorie or weight plan. This tool reports three established estimates so you can compare them: the Mifflin-St Jeor equation (the modern standard), the revised Harris-Benedict equation (the historic reference), and Katch-McArdle, which uses your lean body mass when you provide a body fat percentage. Both metric and imperial units are supported.

How to Use

1. Choose metric (cm/kg) or imperial (ft-in/lb) units. 2. Select your sex and enter age, height, and weight. 3. Optionally tick the body-fat box and set your percentage to unlock the Katch-McArdle estimate. 4. Read your BMR - the large number is the Mifflin-St Jeor result, with the other formulas shown alongside for comparison.

Formula & Definition

Mifflin-St Jeor (primary): Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5 Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161 Harris-Benedict (revised, reference): Men: 88.362 + 13.397 x kg + 4.799 x cm - 5.677 x age Women: 447.593 + 9.247 x kg + 3.098 x cm - 4.33 x age Katch-McArdle (needs body fat %): 370 + 21.6 x lean mass(kg). For example, a 30-year-old man at 175 cm and 70 kg has a Mifflin-St Jeor BMR of about 1,649 kcal.

Interpreting Results

Your BMR is the energy you would burn lying in bed all day - it is not how much you should eat. To find daily needs, multiply BMR by an activity factor to get your TDEE (use the TDEE calculator). The three estimates usually fall within a few percent of each other; Mifflin-St Jeor is the most reliable for the general population, while Katch-McArdle is better for lean, muscular people because it works from lean mass. Treat the figure as a baseline and refine it by tracking your weight over a few weeks.

Frequently Asked Questions

What is BMR? ▾

Basal Metabolic Rate is the calories your body burns at complete rest to sustain life - breathing, circulation, temperature, and cell repair.

Which equation should I trust? ▾

Mifflin-St Jeor is the most accurate for most people. If you know your body fat %, Katch-McArdle can be more accurate because it is based on lean mass.

Is BMR the number of calories I should eat? ▾

No. BMR is energy at rest. Multiply it by an activity factor to get your total daily energy expenditure (TDEE), which reflects how much you actually burn.

Why does my BMR fall as I age? ▾

Resting metabolism tends to decline with age as muscle mass decreases, which is why the equations subtract more for older ages.

This tool provides a general estimate, not individual medical or nutritional advice. Metabolic rate varies between individuals. If you have a health condition or plan a major diet change, consult a doctor or registered dietitian.