BMR & TDEE Calculator - Mifflin-St Jeor With Macros

Two numbers, six outputs

BMR is how many calories your body burns at complete rest - just to keep your heart beating, lungs breathing and cells dividing. Multiply BMR by an activity factor and you get TDEE: the total calories you actually burn in a day. This calculator uses the Mifflin-St Jeor equation (the most accurate for most adults), applies your activity level, adjusts for your goal, and splits the result into protein, fat and carbohydrate grams.

How to calculate BMR and TDEE - step by step

Weight - enter your body weight in kilograms. Morning weight on an empty stomach is the most reliable baseline.
Height - enter your height in centimeters, measured barefoot.
Age - your age in years. BMR declines roughly 1-2% per decade after 20.
Sex - select female or male. The Mifflin-St Jeor formula uses different constants for each.
Activity level - pick the option that best matches your weekly training and daily movement. Most desk workers are sedentary or lightly active.
Goal - cutting subtracts 500 kcal, bulking adds 300 kcal, maintenance keeps TDEE as-is.
Read the results - BMR, TDEE, goal calories plus a macro split (protein, fat, carbs in grams).

The Mifflin-St Jeor formula

Published in 1990 and widely regarded as the most accurate predictive equation for BMR in healthy adults:

Sex	Formula
Male	BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - +5
Female	BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - -161

TDEE = BMR x activity multiplier. The multipliers range from 1.2 (sedentary) to 1.9 (extremely active).

Activity multipliers

Level	Multiplier	Description
Sedentary	1.2	Desk job, no structured exercise
Lightly active	1.375	Training 1-2 times per week
Moderately active	1.55	Training 3-5 times per week
Very active	1.725	Training 6-7 times per week
Extremely active	1.9	Twice-daily training or physical job + training

Practical examples

Example 1: Male, 80 kg, 180 cm, 30 years, moderately active, maintenance. BMR = 1,780 kcal. TDEE = 1,780 x 1.55 = 2,759 kcal. Protein: 160 g, Fat: 77 g, Carbs: 357 g.

Example 2: Female, 60 kg, 165 cm, 25 years, lightly active, cutting. BMR = 1,345 kcal. TDEE = 1,849 kcal. Goal: 1,349 kcal (-500). Protein: 120 g, Fat: 37 g, Carbs: 134 g.

Example 3: Male, 70 kg, 175 cm, 22 years, very active, bulking. BMR = 1,689 kcal. TDEE = 2,914 kcal. Goal: 3,214 kcal (+300). Protein: 140 g, Fat: 89 g, Carbs: 463 g.

Example 4: Female, 90 kg, 170 cm, 45 years, sedentary, cutting. BMR = 1,577 kcal. TDEE = 1,892 kcal. Goal: 1,392 kcal. Protein: 180 g, Fat: 39 g, Carbs: 80 g.

Example 5: Male, 100 kg, 185 cm, 35 years, extremely active, maintenance. BMR = 1,986 kcal. TDEE = 1,986 x 1.9 = 3,773 kcal. Protein: 200 g, Fat: 105 g, Carbs: 507 g.

FAQ - Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the calories your body burns at absolute rest - lying still, doing nothing. TDEE adds your daily activity on top: walking, working, exercising. For most people TDEE is 20-90% higher than BMR.

Why Mifflin-St Jeor and not Harris-Benedict?

The Mifflin-St Jeor equation, published in 1990, predicts BMR within 5% of measured values in most adults. The older Harris-Benedict formula (1919, revised 1984) tends to overestimate by 5-15%, especially in overweight individuals.

Is a 500 kcal deficit safe?

A 500 kcal daily deficit leads to roughly 0.45 kg (1 lb) of fat loss per week. This is widely considered a sustainable, safe rate. Larger deficits can cause muscle loss, fatigue and metabolic adaptation. Never go below your BMR without medical supervision.

Why is protein set at 2g per kg?

Research supports 1.6 - 2.2 g/kg for individuals who exercise regularly and want to preserve or build muscle. The calculator uses 2.0 g/kg as a practical middle ground. Sedentary individuals can go lower (0.8 - 1.2 g/kg).

How do I pick the right activity level?

Most people overestimate their activity. If you sit at a desk 8 hours and go to the gym 3 times per week, you are lightly active, not moderately active. Count structured exercise sessions per week and factor in daily steps. Under 5,000 steps/day with 3 gym sessions = lightly active.

Can carbs go negative?

In extreme cases (very heavy person on a deep cut), the math can produce negative carbs because protein alone exceeds the calorie target. If carbs drop below 50 g, consider reducing the deficit or lowering protein to 1.6 g/kg.

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