What is the Mifflin-St Jeor formula?

The Mifflin-St Jeor formula calculates Basal Metabolic Rate from weight (kg), height (cm), age, and sex. For men: BMR = 10W + 6.25H − 5A + 5. For women: BMR = 10W + 6.25H − 5A − 161. It is the most widely validated BMR equation for the general population.

Is BMR the same as calories burned at rest?

Yes. BMR represents the minimum calories needed to sustain life functions — breathing, circulation, cell repair — while at complete rest. It does not include calories burned through movement or exercise.

Does this calculator work for both men and women?

Yes. The Mifflin-St Jeor equation uses a sex-specific constant: +5 for men and −161 for women. Select your sex in the calculator and the correct formula is applied automatically.

How is BMR different from TDEE?

BMR is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor to account for daily movement and exercise. Most people's TDEE is 20–90% higher than their BMR depending on activity level.

BMR Calculator

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What This Calculator Does

Calculate your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest — using the Mifflin-St Jeor equation, the most widely validated formula for men and women.

It combines Sex, Age, Weight, Height to estimate Estimated BMR, Calories at Complete Rest, Reference Weight.

Formula & Method

The Mifflin-St Jeor BMR formulas: Men:

BMR = 10 \times weight_{kg} + 6.25 \times height_{cm} - 5 \times age + 5

Women:

BMR = 10 \times weight_{kg} + 6.25 \times height_{cm} - 5 \times age - 161

Where weight is in kilograms, height is in centimeters, and age is in years. To convert: divide pounds by 2.2046 for kg; multiply inches by 2.54 for cm.

Notation used in the formulas: $R$ = Estimated BMR; $x_{1}$ = Sex; $x_{2}$ = Age; $x_{3}$ = Weight; $x_{4}$ = Height.

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use BMR as the foundation for calorie budgeting and weight management. Multiply by an activity factor to get TDEE (Total Daily Energy Expenditure), then adjust for your goal.

Worked Examples

Example: 35-year-old woman, 165 cm, 68 kg

BMR = 10(68) + 6.25(165) − 5(35) − 161 = 680 + 1,031.25 − 175 − 161 = 1,375 kcal/day This is the calorie level needed to sustain basic functions at complete rest.

Example: 28-year-old man, 180 cm, 82 kg

BMR = 10(82) + 6.25(180) − 5(28) + 5 = 820 + 1,125 − 140 + 5 = 1,810 kcal/day

BMR vs TDEE: What's the Difference?

BMR is your calorie burn at complete rest — if you stayed in bed all day, your body would use approximately this many calories to maintain organ function, body temperature, and cellular repair.

TDEE (Total Daily Energy Expenditure) adds activity on top of BMR. Multiply your BMR by an activity factor: sedentary (×1.2), lightly active (×1.375), moderately active (×1.55), very active (×1.725), or extra active (×1.9). Use the TDEE calculator to compute this automatically.

Common Mistakes

Confusing BMR with TDEE — BMR is calories burned at rest only; TDEE includes all activity.
Entering weight in pounds or height in inches without converting to metric first (divide lbs by 2.2046 for kg; multiply inches by 2.54 for cm).
Using the male constant (+5) for a female input, or vice versa — the sex-specific constant changes the result by 166 kcal/day.

When Not To Use This Calculator

Elite athletes or bodybuilders with unusually high muscle mass — Mifflin-St Jeor tends to underestimate BMR for very high lean body mass.
Individuals with thyroid conditions, metabolic disorders, or significant hormonal imbalances — consult a clinician for personalized energy needs.

Frequently Asked Questions

What is the Mifflin-St Jeor formula?: The Mifflin-St Jeor formula calculates Basal Metabolic Rate from weight (kg), height (cm), age, and sex. For men: BMR = 10W + 6.25H − 5A + 5. For women: BMR = 10W + 6.25H − 5A − 161. It is the most widely validated BMR equation for the general population.
Is BMR the same as calories burned at rest?: Yes. BMR represents the minimum calories needed to sustain life functions — breathing, circulation, cell repair — while at complete rest. It does not include calories burned through movement or exercise.
Does this calculator work for both men and women?: Yes. The Mifflin-St Jeor equation uses a sex-specific constant: +5 for men and −161 for women. Select your sex in the calculator and the correct formula is applied automatically.
How is BMR different from TDEE?: BMR is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor to account for daily movement and exercise. Most people's TDEE is 20–90% higher than their BMR depending on activity level.

Inputs Used

Sex: Used directly in the calculation.
Age: Used directly in the calculation.
Weight: Used directly in the calculation.
Height: Used directly in the calculation.

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