Calculate Your BMR

Calculating your BMR is the first step toward understanding your daily calorie needs. This guide walks you through the Mifflin-St Jeor equation step by step, with worked examples for both men and women. Once you understand the math, you can use our BMR calculator for instant results.

What is BMR calculation?

BMR calculation estimates how many calories your body burns at complete rest to maintain basic life functions. The result is expressed in kilocalories per day (kcal/day). This number represents the minimum energy your body needs if you were to lie still all day — your heart beating, lungs breathing, brain functioning, and cells repairing.

The most widely accepted formula for BMR calculation is the Mifflin-St Jeor equation, published in 1990. It was developed using modern metabolic data and is considered the gold standard for predictive BMR estimation.

Mifflin-St Jeor formula walkthrough

The Mifflin-St Jeor equation has two versions — one for men and one for women:

For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5

For women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Each part of the formula contributes something:

• 10 × weight(kg): weight component — heavier bodies need more energy
• 6.25 × height(cm): height component — taller bodies have more tissue
• − 5 × age: age component — metabolism slows with age
• + 5 (men) or − 161 (women): sex adjustment — accounts for average differences in body composition

Example calculation for a man

Let us walk through a real example:

Profile: 30-year-old man, 80 kg, 180 cm

Step 1: 10 × 80 = 800 (weight component)

Step 2: 6.25 × 180 = 1,125 (height component)

Step 3: − 5 × 30 = −150 (age component)

Step 4: + 5 (sex adjustment for men)

Result: 800 + 1,125 − 150 + 5 = 1,780 kcal/day

Verify this with our BMR calculator — the result should match closely.

Example calculation for a woman

Profile: 30-year-old woman, 65 kg, 165 cm

Step 1: 10 × 65 = 650 (weight component)

Step 2: 6.25 × 165 = 1,031 (height component)

Step 3: − 5 × 30 = −150 (age component)

Step 4: − 161 (sex adjustment for women)

Result: 650 + 1,031 − 150 − 161 = 1,370 kcal/day

Example for a middle-aged person

Profile: 50-year-old man, 90 kg, 178 cm

Step 1: 10 × 90 = 900

Step 2: 6.25 × 178 = 1,113

Step 3: − 5 × 50 = −250

Step 4: + 5

Result: 900 + 1,113 − 250 + 5 = 1,768 kcal/day

Notice how the age component (−250 at age 50 vs −150 at age 30) reduces the BMR by 100 calories — a direct effect of aging on metabolism.

Using BMR results for your goals

Once you have your BMR, you can use it to plan your nutrition:

• Weight loss: Multiply BMR by your activity factor to get TDEE, then subtract 250–500 calories. See the calorie deficit guide.
• Weight gain: Add 250–500 calories to TDEE for a lean surplus. See the calorie surplus guide.
• Maintenance: Eat at TDEE. Use the maintenance calories calculator for a quick estimate.

For a complete daily plan, combine your BMR with the macro calculator to determine protein, carb, and fat targets.

Tips for accurate BMR calculation

1. Use accurate measurements: Weigh yourself in the morning after using the bathroom, before eating or drinking. Measure height without shoes.
2. Be honest about your age: The age component has a real impact — do not understate your age to get a higher result.
3. Know your activity level: Your BMR is only the resting component. For total daily needs, you must apply an activity factor.
4. Recalculate after weight changes: A 5 kg change in body weight shifts your BMR by roughly 50 calories. Recalculate regularly.
5. Use the BMR calculator for convenience: Our BMR calculator handles all the math instantly and supports both metric and imperial units.

Related tools

• BMR Calculator — get your BMR instantly
• TDEE Calculator — find your total daily energy expenditure
• Macro Calculator — split calories into protein, carbs, and fats
• BMR Equations Guide — compare Mifflin-St Jeor vs Harris-Benedict
• Maintenance Calories Calculator — find your daily target