What is the Mifflin-St Jeor equation?

Developed by M.D. Mifflin and S.T. St Jeor in 1990, the formula estimates Basal Metabolic Rate as: Men: (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: (10 × kg) + (6.25 × cm) − (5 × age) − 161. It is recommended by the Academy of Nutrition and Dietetics as the most accurate predictive equation for most adults.

How is Mifflin-St Jeor different from Harris-Benedict?

The Mifflin-St Jeor equation (1990) tends to be 5–10% more accurate than the original Harris-Benedict equation (1919) for modern adults, particularly for people who are overweight. Harris-Benedict was revised in 1984 to reduce its systematic overestimation.

What is TDEE and how is it calculated?

Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor: Sedentary × 1.2, Lightly active × 1.375, Moderately active × 1.55, Very active × 1.725, Extra active × 1.9. TDEE represents the total calories you burn each day including movement and exercise.

How accurate is the Mifflin-St Jeor estimate?

Population-level estimates typically fall within 10–20% of measured resting metabolic rate for individuals. Factors like muscle mass, genetics, hormones, and medication can shift actual needs. Use the result as a baseline and adjust by 100–200 kcal if real-world weight response does not match expectations.

How many calories should I cut to lose weight?

A deficit of 500 kcal/day below TDEE targets approximately 0.5 kg (1 lb) of fat loss per week. Deficits above 1,000 kcal/day increase the risk of muscle loss and nutrient shortfalls and are not recommended without medical oversight.

Does BMR change over time?

Yes. BMR decreases with age and drops when body weight falls (due to less metabolically active tissue). Resistance training that builds muscle can partially offset this decline. Re-calculate your BMR whenever your weight changes by more than 5 kg or your activity level shifts significantly.

Mifflin-St Jeor BMR Calculator

Name: Mifflin-St Jeor BMR Calculator
Availability: InStock
Author: Nham Vu

Enter your age, sex, height, and weight to calculate your BMR and TDEE using the clinically preferred Mifflin-St Jeor equation.

Your Details

Unit System

Biological Sex

Age (years)

Height (cm)

Weight (kg)

Activity Level

Fill in your details and click Calculate to see your BMR and TDEE.

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Summary

Enter your age, sex, height, and weight to calculate your BMR and TDEE using the clinically preferred Mifflin-St Jeor equation.

How it works

Select your biological sex and preferred unit system.
Enter your age, height, and weight.
Choose your typical daily activity level.
Click Calculate to apply the Mifflin-St Jeor formula: (10 × kg) + (6.25 × cm) − (5 × age) ± constant.
Your BMR and TDEE are shown alongside calorie targets for each weight goal.
Copy any value with the Copy button for use in a meal planner or spreadsheet.

Use cases

Set a science-based daily calorie budget for weight loss.
Determine maintenance calories before adjusting macros.
Establish a calorie surplus for muscle gain.
Understand how activity level scales your resting calorie burn.
Compare calorie needs across different activity scenarios.
Help clients establish calorie targets as a dietitian or personal trainer.
Track how TDEE shifts with age or significant weight change.
Validate calorie estimates from wearables or fitness apps.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu