BMR (Basal Metabolic Rate) is the amount of energy your body needs at complete rest to maintain vital functions such as breathing, circulation, and cell production. It does not include calories burned from daily activities or exercise.

Which BMR formula is the most accurate?

For most people, the Mifflin-St Jeor equation is considered the most accurate modern formula. Harris-Benedict is older and tends to overestimate slightly. Katch-McArdle can be very accurate if you know your body fat percentage, because it uses lean body mass.

How do I use BMR to lose weight?

First estimate your TDEE (total daily energy expenditure) by multiplying your BMR by an activity factor. Then create a calorie deficit of about 300–500 kcal per day below your TDEE. This usually leads to a weight loss of around 0.25–0.5 kg per week for most adults.

How often should I recalculate my BMR?

Recalculate your BMR whenever your weight changes by more than about 5 kg (10 lb), when your body fat changes significantly, or at least every few months if you are actively changing your body composition.

Is BMR the same as resting metabolic rate (RMR)?

They are closely related but not identical. BMR is measured under very strict laboratory conditions after 8+ hours of sleep and 12 hours of fasting. RMR is slightly less strict and usually a bit higher. In practice, many online tools use the terms interchangeably.

BMR Calculator (Basal Metabolic Rate)

Estimate your basal metabolic rate and daily calorie needs using multiple evidence-based formulas, then tailor targets for weight loss, maintenance, or muscle gain.

BMR & Daily Calorie Calculator

Units:

Sex at birth

Age

years

Height

Weight

Body fat (optional)

% body fat

If provided, we also calculate BMR using the Katch–McArdle formula based on lean body mass.

Activity level

Goal

Your Results

BMR (Mifflin–St Jeor)

0 kcal/day

Widely used modern equation for most adults.

BMR (Harris–Benedict)

0 kcal/day

Classic equation, tends to be slightly higher.

BMR (Katch–McArdle)

— kcal/day

Uses lean body mass. Shown when body fat is provided.

Daily calorie needs (based on Mifflin–St Jeor)

Activity factor (TDEE): 0 kcal/day
Suggested target for your goal: 0 kcal/day
Estimated weekly change: 0
Approx. daily deficit/surplus: 0 kcal/day

How to interpret this

Your BMR is the energy your body needs at complete rest. Your TDEE (total daily energy expenditure) includes your usual activity level.

To change your weight, adjust your average daily intake relative to your TDEE. A difference of about 500 kcal/day typically corresponds to roughly 0.5 kg (1 lb) of weight change per week, but individual responses vary.

What is BMR (Basal Metabolic Rate)?

Basal Metabolic Rate (BMR) is the number of calories your body needs each day to keep you alive at complete rest – to power your heart, lungs, brain, liver, kidneys, and all the basic processes that keep you functioning.

BMR does not include calories burned from walking, working, training, or digestion. When you multiply BMR by an activity factor, you get your TDEE (Total Daily Energy Expenditure), which is the key number for planning weight loss, maintenance, or muscle gain.

BMR formulas used in this calculator

This tool calculates BMR using three evidence-based equations and shows them side by side.

1. Mifflin–St Jeor equation (default)

Considered one of the most accurate formulas for modern lifestyles.

For men:

\(\text{BMR} = 10 \times \text{weight}_{kg} + 6.25 \times \text{height}_{cm} - 5 \times \text{age}_{years} + 5\)

For women:

\(\text{BMR} = 10 \times \text{weight}_{kg} + 6.25 \times \text{height}_{cm} - 5 \times \text{age}_{years} - 161\)

2. Revised Harris–Benedict equation

An older but still widely used formula. It often gives slightly higher values than Mifflin–St Jeor.

For men:

\(\text{BMR} = 13.397 \times \text{weight}_{kg} + 4.799 \times \text{height}_{cm} - 5.677 \times \text{age}_{years} + 88.362\)

For women:

\(\text{BMR} = 9.247 \times \text{weight}_{kg} + 3.098 \times \text{height}_{cm} - 4.330 \times \text{age}_{years} + 447.593\)

3. Katch–McArdle equation (uses body fat)

If you know your body fat percentage, this formula can be very accurate because it uses lean body mass instead of total weight.

First estimate lean body mass (LBM):

\(\text{LBM}_{kg} = \text{weight}_{kg} \times (1 - \text{body fat fraction})\)

Then:

\(\text{BMR} = 370 + 21.6 \times \text{LBM}_{kg}\)

From BMR to TDEE (Total Daily Energy Expenditure)

To estimate how many calories you burn on a typical day, we multiply your BMR by an activity factor:

Sedentary (1.2): desk job, little or no exercise
Lightly active (1.375): light exercise 1–3 days/week
Moderately active (1.55): moderate exercise 3–5 days/week
Very active (1.725): hard exercise 6–7 days/week
Extra active (1.9): very hard training + physical job

\(\text{TDEE} \approx \text{BMR} \times \text{activity factor}\)

How to use BMR for weight loss, maintenance, or muscle gain

This calculator suggests a calorie target based on your goal:

Maintain weight: target ≈ TDEE
Mild weight loss (~0.25 kg/week): target ≈ TDEE − 250 kcal/day
Weight loss (~0.5 kg/week): target ≈ TDEE − 500 kcal/day
Mild gain (~0.25 kg/week): target ≈ TDEE + 250 kcal/day
Muscle gain (~0.5 kg/week): target ≈ TDEE + 500 kcal/day

These are typical starting points. Your actual progress will depend on genetics, sleep, stress, hormones, training quality and how accurately you track intake.

Limitations and safety notes

BMR equations provide estimates, not exact values.
They are designed for adults; they are not appropriate for children without professional guidance.
Very low-calorie diets should only be followed under medical supervision.
If you have chronic illness, are pregnant, breastfeeding, or underweight, consult a healthcare professional before making major changes.