BMR Calculator

Estimate your Basal Metabolic Rate using the Mifflin-St Jeor equation

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What Is BMR?

BMR stands for Basal Metabolic Rate: the number of calories your body burns at complete rest, just to keep your vital organs, brain, heart and muscles running. It does not include any activity, exercise, or digestion of food; it is the minimum energy your body needs to simply stay alive over 24 hours. For most people, BMR makes up 60–70% of total daily calorie burn, which is why it’s the essential starting point for any calorie or weight-management calculation.

How This Calculator Works

This calculator uses the Mifflin-St Jeor equation, the formula most widely recommended by dietitians and nutrition researchers as the most accurate for estimating BMR in the general population:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age (years) + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age (years) – 161

Enter your biological sex, age, height and weight above and click Calculate to see your BMR, plus a full breakdown of your real daily calorie needs at every activity level, from sedentary to very active.

Why This Calculator Has No Activity Level Field

Unlike a TDEE calculator, a BMR calculator deliberately leaves activity out of the equation – BMR is, by definition, your resting energy burn with zero activity included. Instead of a single activity-adjusted number, we show you the full reference table above so you can see your real calorie needs at every activity level at a glance, without having to recalculate for each one. If you’d rather get a single number tailored to your own real activity level and weight goal, use our TDEE Calculator instead.

What Affects Your BMR?

BMR isn’t fixed – several real factors move it up or down:

• Muscle mass – muscle tissue burns more calories at rest than fat tissue, so a more muscular body generally has a higher BMR.
• Age – BMR naturally declines with age, largely due to a gradual loss of muscle mass over time.
• Sex – men typically have a higher BMR than women of the same age, height and weight, largely due to differences in average muscle mass, which the Mifflin-St Jeor formula accounts for directly.
• Genetics – individual metabolic rate varies by hereditary factors that a formula like this can’t capture.
• Body size – a larger body, taller or heavier, generally has a higher BMR simply because it has more tissue to maintain.

BMR vs TDEE: What’s the Difference?

Your BMR is the calories you’d burn lying in bed all day with nothing to digest. Your TDEE adds real activity and the energy used to digest food on top of that, so TDEE is always equal to or higher than BMR. For a fuller breakdown of how the two relate and which one you should actually use to plan your calories, read BMR vs TDEE: Which Number Actually Matters?, or calculate your own personalised, activity-adjusted number with our TDEE Calculator.

Frequently Asked Questions

What is a normal BMR?

There is no single “normal” BMR – it depends on your sex, age, height and weight. A typical adult BMR generally falls somewhere between 1,300 and 2,000 kcal/day, but the only accurate figure is the one calculated from your own real measurements above.

Is a higher BMR better?

A higher BMR generally means you can eat more calories while maintaining your weight, since your body burns more at rest. It’s usually a sign of greater muscle mass, larger body size, or younger age, rather than something to chase on its own.

Can I increase my BMR?

Yes, to a degree. Building muscle through resistance training is the most reliable, evidence-based way to raise your BMR over time, since muscle tissue burns more calories at rest than fat tissue.

Does BMR include exercise?

No. BMR is your resting energy burn only, with zero activity included. Calories burned through exercise, walking and daily movement are added on top of BMR to calculate your full TDEE (Total Daily Energy Expenditure).

Why do BMR calculators give different results?

Different calculators often use different formulas – commonly Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle – each with slightly different assumptions, which produces slightly different results. Mifflin-St Jeor, the formula this calculator uses, is generally regarded as the most accurate for the general population.

Want to see the maths worked through by hand? Read How to Calculate Your BMR (Step by Step).

Related Calculators

• TDEE Calculator – your full daily calorie needs, adjusted for real activity level and weight goal
• Food Calorie Calculator – search 5,200+ UK foods and build a meal against your daily target