BMR / TDEE Calculator

Calculate your Basal Metabolic Rate and daily calorie needs. Three formulas, five activity levels. Everything runs in your browser.

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Mifflin-St Jeor Is the Most Accurate for Most People

A 2005 meta-analysis by the American Dietetic Association found Mifflin-St Jeor to be the most reliable BMR formula for the general population, within 10% accuracy for 82% of subjects tested.

TDEE Is Your Maintenance Calories

TDEE represents the total calories you burn in a day, including exercise. Eating at your TDEE maintains your current weight. Eat less to lose weight, more to gain. A 500 kcal daily deficit results in roughly 0.5 kg (1 lb) of weight loss per week.

Know Your Body Fat? Use Katch-McArdle

Katch-McArdle uses lean body mass instead of total weight, making it more accurate for athletes and muscular individuals. If you know your body fat percentage from a DEXA scan or caliper test, this formula adapts to your specific body composition.

Activity Level Is the Biggest Variable

Most people overestimate their activity level. A desk job with 3 gym sessions per week is "Lightly Active", not "Moderately Active". When in doubt, choose one level lower and adjust based on real-world results over 2-4 weeks.

Common Use Cases

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Weight Loss Planning

Calculate your TDEE and subtract 250-500 kcal to create a sustainable caloric deficit for gradual fat loss.

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Muscle Building

Add 250-500 kcal above your TDEE to fuel muscle growth during a strength training program.

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Meal Planning

Use your TDEE as a daily calorie target to plan balanced meals and track macronutrient intake.

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Fitness Assessment

Compare BMR across different formulas to understand your metabolic baseline and monitor changes over time.

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Health Monitoring

Track your BMR alongside body composition changes to ensure your metabolism stays healthy during a diet.

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Comparing Formulas

See how Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle differ for your specific body stats to choose the most appropriate estimate.

Frequently Asked Questions

What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest just to maintain basic functions like breathing, circulation, and cell production. TDEE (Total Daily Energy Expenditure) includes BMR plus all additional calories burned through daily activities and exercise. TDEE = BMR x Activity Multiplier.
Which formula should I use?
For most people, Mifflin-St Jeor is the best choice — it is the most accurate for the general population according to research. If you know your body fat percentage (from a DEXA scan or caliper test), Katch-McArdle will give a more personalized result. Harris-Benedict is the classic formula and still widely used, but slightly less accurate on average.
How do I choose my activity level?
Be honest and conservative. Sedentary: desk job, no exercise. Lightly Active: desk job with 1-3 light workouts per week. Moderately Active: active job or 3-5 moderate workouts. Very Active: physical job plus daily exercise. Extra Active: professional athlete or very demanding physical labor plus training.
Is my data processed in my browser?
Yes. All calculations are performed entirely in your browser using JavaScript. Your height, weight, age, and other data are never sent to any server. You can verify this by disconnecting from the internet — the calculator continues to work.
How accurate are these calculations?
BMR formulas estimate within 10% for most individuals. Actual metabolic rate varies based on genetics, hormones, muscle mass, and other factors. Use the calculated TDEE as a starting point, then adjust based on real-world results over 2-4 weeks.
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