BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest - just to keep your organs functioning. It accounts for about 60–70% of total calorie expenditure. BMR increases with more muscle mass and decreases with age.

TDEE (Total Daily Energy Expenditure) is the total number of calories you burn in a day, including physical activity. It is calculated by multiplying your BMR by an activity multiplier ranging from 1.2 (sedentary) to 1.9 (extremely active).

Which formula is more accurate - Mifflin-St Jeor or Harris-Benedict?

The Mifflin-St Jeor equation (1990) is generally considered more accurate for most people - studies show it predicts resting metabolic rate within about 10% for the majority of individuals. The original Harris-Benedict formula (1919) tends to overestimate slightly. Both are estimates; individual metabolism can vary significantly.

How many calories should I eat to lose weight?

A deficit of approximately 500 calories per day leads to roughly 1 lb (0.45 kg) of weight loss per week. A 250-calorie deficit targets about 0.5 lb per week. Larger deficits can work short-term but may lead to muscle loss and metabolic adaptation. Aim for at least 1,200 kcal/day for women and 1,500 kcal/day for men as a minimum.

Why does activity level affect calorie needs so much?

A sedentary person burns calories mainly through BMR. A very active person might burn 50–60% more calories per day through exercise and daily movement (NEAT - non-exercise activity thermogenesis). This is why two people with the same BMR can have very different TDEE values.

BMR & TDEE Calculator

What is BMR?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest: the energy needed to keep your heart beating, lungs breathing, and organs functioning. BMR typically accounts for 60–70% of total daily energy expenditure.

What is TDEE?

Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor that reflects how much you move throughout the day. A sedentary person (1.2×) burns far fewer calories than someone with a physically demanding job (1.9×).

Mifflin-St Jeor vs Harris-Benedict

The Mifflin-St Jeor equation (1990) is the more modern formula and is recommended by most dietitians as the most accurate for general use. The Harris-Benedict equation (revised 1984) tends to overestimate BMR by about 5% on average. Both are estimates; individual metabolism varies by genetics, muscle mass, hormones, and more.

Activity level multipliers

Level	Description	Multiplier
Sedentary	Little or no exercise	1.2×
Lightly active	Exercise 1–3 days/week	1.375×
Moderately active	Exercise 3–5 days/week	1.55×
Very active	Hard exercise 6–7 days/week	1.725×
Extra active	Physical job or 2× training/day	1.9×

Caloric targets for goals

Once you know your TDEE, you can set a caloric target based on your goal:

Maintain weight: eat at TDEE.
Lose weight (~1 lb/week): eat at TDEE − 500 kcal/day. A 500 kcal daily deficit equals ~3,500 kcal/week, approximately one pound of fat.
Lose weight (~0.5 lb/week): eat at TDEE − 250 kcal/day. More sustainable for most people; better preserves muscle mass.
Lean bulk (+0.5 lb muscle/week): eat at TDEE + 200–300 kcal/day. A modest surplus minimizes fat gain while supporting muscle growth.

These are starting estimates. Adjust based on real-world results after 2–3 weeks, since individual metabolic variation means actual weight change often differs from predictions.

Katch-McArdle formula

A third BMR formula - the Katch-McArdle equation - calculates BMR from lean body mass (LBM) rather than total body weight:

BMR = 370 + (21.6 × LBM in kg)

where LBM = total weight × (1 − body fat fraction). Because it accounts for muscle mass directly, the Katch-McArdle formula is the most accurate for athletes and highly muscular individuals, who would otherwise be overestimated by Mifflin-St Jeor or Harris-Benedict. You need to know your body fat percentage to use it (see the Body Fat Calculator).