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BMR Calculator

Find your metabolic rate

Uses the Mifflin-St Jeor formula.

Weight70 kg
30 kg200 kg
Height
100 cm170 cm220 cm
Age30 years
1580
Gender
Activity Level

BMR

1,618 kcal/day

calories your body burns at complete rest

TDEE — Moderate

2,507 kcal/day

For Weight Loss (−500 kcal)

2,007 kcal/day

For Muscle Gain (+300 kcal)

2,807 kcal/day

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Your body burns 1,618 kcal just to stay alive. Eat close to your TDEE on rest days and add workout calories on active days.

🔥 Health tool

How many calories does
your body burn at rest?

Enter your weight, height, age, and gender to instantly estimate your Basal Metabolic Rate — the calories your body needs just to stay alive each day.

Daily BMRCalorie baselineMifflin-St Jeor formulaWeight & height inputFree & instant

Step by step

How to use the BMR Calculator

1

Enter your weight

Type your current body weight in kilograms.

2

Enter your height

Enter your height in cm or switch to feet/inches.

3

Add age and gender

Enter your age and set the gender field (1 for male, 0 for female).

4

Get your BMR

Instantly see your daily BMR in kcal — the calorie floor your body needs just to function.

Why use this calculator?

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Set a calorie target

BMR is the foundation for calorie tracking. Multiply it by your activity factor using the Calorie Calculator to find your total daily energy expenditure.

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Weight loss planning

To lose weight, you need to eat fewer calories than your total daily expenditure. Knowing your BMR makes this calculation accurate instead of guesswork.

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Muscle gain diet

Building muscle requires a calorie surplus. Your BMR tells you the minimum you need before adding training calories on top.

How BMR is calculated — the Mifflin-St Jeor formula

BMR represents the calories your body burns just to keep you alive — maintaining heart rate, breathing, body temperature, and cell repair. This is typically 60–75% of your total daily calorie expenditure. Even if you did absolutely nothing all day, you would still burn your BMR in calories. This is why very low calorie diets (below BMR) are dangerous: they force the body to break down muscle and organ tissue for fuel.

To find your Total Daily Energy Expenditure (TDEE) — the actual calories you burn in a day including activity — multiply your BMR by an activity factor: 1.2 for sedentary (desk job, no exercise), 1.375 for lightly active (exercise 1–3 days/week), 1.55 for moderately active (exercise 3–5 days/week), 1.725 for very active (hard exercise 6–7 days/week). Use the Calorie Calculator on this site to compute your TDEE directly from your BMR.

BMR declines with age, primarily because muscle mass decreases after age 30. Every kilogram of muscle burns roughly 13 kcal/day at rest, while a kilogram of fat burns only about 4.5 kcal/day. This is the physiological reason why strength training is the most effective long-term weight management strategy — it maintains or increases BMR by preserving muscle mass. Cardio burns calories during exercise but does not significantly raise BMR the way resistance training does.

Formula

Male BMR = (10 × W) + (6.25 × H) − (5 × A) + 5 | Female BMR = (10 × W) + (6.25 × H) − (5 × A) − 161

W is weight in kilograms. H is height in centimetres. A is age in years. The Mifflin-St Jeor equation is considered more accurate than the older Harris-Benedict formula for most modern adults. The result is calories per day burned at complete rest — your body’s minimum calorie floor.

Worked example

Male, 30 years old, 75 kg, 175 cm: BMR = (10 × 75) + (6.25 × 175) − (5 × 30) + 5 = 750 + 1093.75 − 150 + 5 = 1698.75 kcal/day. Female, 28 years old, 60 kg, 162 cm: BMR = (10 × 60) + (6.25 × 162) − (5 × 28) − 161 = 600 + 1012.5 − 140 − 161 = 1311.5 kcal/day.

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What is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate is the minimum number of calories your body requires to sustain its core functions while at complete rest — think of it as the energy an engine consumes just sitting idle. These functions include keeping the heart beating, the brain active, the kidneys filtering, the lungs breathing, and every cell in the body maintained. For most people, BMR accounts for roughly 70% of total daily calorie burn. Physical activity contributes around 20%, and the remaining 10% goes toward digesting food — a process known as the thermic effect of food.

A true BMR measurement is taken under very strict conditions: the person must be fully awake but completely at rest, in a neutral temperature environment, with the digestive system inactive. Because these conditions are difficult to replicate outside a clinical setting, most calculators — including this one — estimate BMR using validated statistical equations.

BMR Equations Explained

Three widely used equations exist for estimating BMR. Each has its own strengths depending on the individual's body composition and available data.

Mifflin-St Jeor Equation (Recommended)

Introduced in 1990, this is currently the most accurate equation for the general population and is the default used by this calculator.

Men

BMR = 10W + 6.25H − 5A + 5

Women

BMR = 10W + 6.25H − 5A − 161

Revised Harris-Benedict Equation

One of the earliest BMR formulas, revised in 1984. Less accurate than Mifflin-St Jeor for most modern adults but still widely referenced.

Men

BMR = 13.397W + 4.799H − 5.677A + 88.362

Women

BMR = 9.247W + 3.098H − 4.330A + 447.593

Katch-McArdle Formula

Unlike the other two, this formula factors in lean body mass, making it more precise for athletes and leaner individuals who know their body fat percentage.

BMR = 370 + 21.6 × (1 − F) × W

W — body weight in kg

H — height in cm

F — body fat percentage

Factors That Influence Your BMR

BMR is not a fixed number — several biological and environmental factors cause it to shift over time.

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Muscle Mass

Aerobic exercise like running does not directly raise BMR. Anaerobic training such as weight lifting builds muscle, and muscle tissue burns more calories at rest than fat tissue — so more muscle means a higher BMR.

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Age

BMR naturally declines with age as muscle mass decreases. After age 30, the body gradually loses muscle if not actively maintained through resistance training, lowering the daily calorie requirement.

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Genetics

Hereditary traits inherited from parents and ancestors play a role in determining baseline metabolic rate. Some people are simply born with faster or slower metabolisms.

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Weather & Temperature

Cold environments push the body to generate more heat, raising BMR. Extreme heat also increases BMR as the body works to cool internal organs. BMR rises approximately 7% for every 1.36°F increase in core body temperature.

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Diet & Eating Patterns

Eating small, regular meals keeps metabolism active. Prolonged starvation or severe calorie restriction can reduce BMR by up to 30% as the body enters a conservation mode — similar to a phone switching to low-power mode.

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Pregnancy

Supporting a growing fetus significantly increases BMR, which is why calorie needs rise during pregnancy. Menopause can also shift BMR up or down depending on hormonal changes.

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Supplements & Stimulants

Certain substances raise BMR temporarily. Caffeine is the most common example, and it is a key ingredient in many weight-loss supplements for this reason.

BMR vs Resting Metabolic Rate (RMR)

BMR and RMR are often used interchangeably, but they are technically different. BMR requires total physiological equilibrium — the person must be completely at rest, awake, and in a fasted state in a controlled environment. RMR (also called Resting Energy Expenditure or REE) is measured under more relaxed conditions and is slightly higher than BMR as a result. For practical purposes such as calorie planning, the difference is small enough that the two terms are treated as equivalent.

How Accurate Are BMR Calculators?

Online BMR calculators provide a useful estimate, but they are not perfectly precise. A 2005 meta-analysis found that even after controlling for all known metabolic variables, there is still a 26% unexplained variance in BMR between individuals. This means two people with identical weight, height, age, and gender can have meaningfully different metabolic rates due to factors science has not yet fully identified.

For a more accurate measurement, a calorimetry device — available at many gyms, clinics, and weight-loss centres — can directly measure your metabolic rate. Consulting a registered dietitian or sports nutritionist is also a reliable option. That said, a calculated BMR is a solid starting point. Tracking your food intake, exercise, and weight changes in a journal over several weeks will reveal how your body actually responds and help you fine-tune your calorie targets far more effectively than any formula alone.

Key takeaway

BMR and TDEE are estimates, not exact values. Use them as a starting framework, then adjust based on real-world results over 2–4 weeks of consistent tracking.

From BMR to Total Daily Energy Expenditure (TDEE)

Your BMR is the calorie floor — the minimum your body needs at rest. To find how many calories you actually need each day, multiply your BMR by an activity factor:

Activity LevelDescriptionMultiplier
SedentaryDesk job, little or no exercise× 1.2
Lightly ActiveLight exercise 1–3 days/week× 1.375
Moderately ActiveModerate exercise 3–5 days/week× 1.55
Very ActiveHard exercise 6–7 days/week× 1.725
Extra ActivePhysical job or twice-daily training× 1.9

Frequently asked questions