BMR Calculator

Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation with TDEE activity multipliers.

The BMR Calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate — the number of calories your body burns at rest to maintain vital functions like breathing, circulation, and cell production. It also calculates your Total Daily Energy Expenditure (TDEE) across five activity levels, helping you plan nutrition for weight loss, maintenance, or muscle gain.

Weight (kg)

Height (cm)

Age (years)

Activity Level

Your data stays in your browser

Tutorial

How to Use the BMR Calculator

Enter Your Details

Input your weight, height, and age. Select your gender for accurate calculation.

Choose Activity Level

Select the activity level that best matches your typical weekly exercise frequency.

Review TDEE Results

See your BMR and TDEE values across all five activity levels for nutritional planning.

Guide

Complete Guide to Basal Metabolic Rate

Understanding Basal Metabolic Rate

BMR represents the minimum calories your body needs to sustain life while at complete rest — as if you were lying in bed all day. It powers breathing, heartbeat, brain function, cell repair, and temperature regulation. For most people, BMR accounts for 60–75% of total daily energy expenditure. Knowing your BMR is the foundation of any evidence-based nutrition plan.

The Mifflin-St Jeor Equation Explained

The Mifflin-St Jeor equation, published in 1990, is considered the most accurate predictive BMR formula by the American Dietetic Association. For males: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5. For females: the same formula but −161 instead of +5. This accounts for the metabolic differences between sexes.

From BMR to TDEE

Total Daily Energy Expenditure (TDEE) adds your physical activity calories to your BMR. The Harris-Benedict activity factors range from 1.2 (sedentary) to 1.9 (very active). Your TDEE is the actual number of calories you burn in a day. To lose weight, eat below TDEE. To gain weight, eat above it. To maintain, match it as closely as possible.

Factors That Affect Your BMR

Several factors influence your BMR beyond weight, height, age, and sex. Muscle mass is the biggest variable — muscle burns more calories at rest than fat. Genetics play a role too, with some people naturally having faster metabolisms. Hormones (especially thyroid), body temperature, caffeine intake, and even climate can all shift your BMR up or down.

Sources

Examples

Worked Examples

Example: Male BMR Calculation

Given: Male, 80 kg, 180 cm, 30 years old, moderate activity.

Step 1: Apply Mifflin-St Jeor (male): 10×80 + 6.25×180 − 5×30 + 5.

Step 2: Calculate: 800 + 1125 − 150 + 5 = 1780 kcal/day.

Step 3: Multiply by moderate factor (1.55): 1780 × 1.55 = 2759 kcal/day TDEE.

Step 4: For weight loss, subtract 500: target = 2259 kcal/day.

Result: BMR = 1780 kcal/day, TDEE = 2759 kcal/day (moderate activity).

Example: Female BMR Calculation

Given: Female, 60 kg, 165 cm, 25 years old, light activity.

Step 1: Apply Mifflin-St Jeor (female): 10×60 + 6.25×165 − 5×25 − 161.

Step 2: Calculate: 600 + 1031.25 − 125 − 161 = 1345 kcal/day.

Step 3: Multiply by light factor (1.375): 1345 × 1.375 = 1850 kcal/day TDEE.

Step 4: For maintenance, target approximately 1850 kcal/day.

Result: BMR = 1345 kcal/day, TDEE = 1850 kcal/day (light activity).

Use Cases

Typical Use Cases

Weight Loss Planning

“Calculate your TDEE to determine how many calories you burn daily, then create a moderate caloric deficit of 300–500 calories below that number. This approach ensures sustainable weight loss of 0.5–1 pound per week without extreme dieting that could slow your metabolism.”

Muscle Building Nutrition

“For muscle gain, you need a caloric surplus above your TDEE. Use the BMR calculator to find your maintenance calories, then add 200–400 calories primarily from protein and complex carbohydrates. Pair this with a structured resistance training program for optimal muscle growth results.”

Athletic Performance Optimization

“Athletes need precise calorie targets to fuel training without gaining unwanted fat. Calculate your BMR and select the appropriate activity level to determine baseline needs. Adjust intake around training days using the TDEE multipliers to match energy expenditure with nutritional support.”

Frequently Asked Questions

?What is the Mifflin-St Jeor equation?

It is the most accurate BMR prediction formula, developed in 1990. For men: 10×weight + 6.25×height − 5×age + 5. For women: same but minus 161 instead.

?What is the difference between BMR and TDEE?

BMR is calories burned at complete rest. TDEE adds your physical activity on top of BMR to give your total daily calorie burn.

?How do I use BMR for weight loss?

Calculate your TDEE, then eat 300–500 calories below it. Never eat below your BMR, as that can slow metabolism and cause nutrient deficiencies.

?Which activity level should I choose?

Be honest about your exercise frequency. Most people with desk jobs who exercise 3 times per week should select Moderate activity level.

?Does BMR change with age?

Yes, BMR decreases approximately 1–2% per decade after age 20 due to loss of muscle mass. Regular strength training helps maintain higher BMR.

?Is this BMR calculator free to use?

Yes, completely free with no registration, no ads, and unlimited calculations. Use it whenever you need to adjust your nutrition plan.

?Is my personal data kept private?

Yes. All calculations run entirely in your browser. No weight, age, or calorie data is sent to any server or stored anywhere.

?How often should I recalculate my BMR?

Recalculate every 4–6 weeks or whenever your weight changes by more than 2–3 kg, as your BMR adjusts with body weight changes.

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