Calorie Deck

BMR Calculator — Basal Metabolic Rate

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest to keep you alive — breathing, circulation, cell repair. For most adults it lands between 1,200 and 2,200 kcal per day and accounts for 60 to 75 percent of total daily burn. BMR is not the number you should eat; multiply it by your activity level to get that.

Leave 0 if you do not know it.

What is bmr calculator?

BMR is measured under strict conditions: lying down, fasting, in a thermally neutral room. You will never actually spend a day in that state, which is why BMR is a building block rather than a target.

Resting metabolic rate (RMR) is measured under slightly looser conditions and runs a little higher. The two terms are often used interchangeably in casual settings.

Roughly speaking, your largest organ by energy use is your brain, followed by liver, muscle and heart. Contrary to popular belief, resting muscle burns modestly — about 13 kcal per kilogram per day.

How BMR is calculated

The Mifflin-St Jeor equation predicts BMR from weight, height, age and sex, and is the current standard in clinical settings. If you know your body fat percentage, the Katch-McArdle equation is often more accurate because it uses lean mass directly rather than estimating body composition from scale weight.

Mifflin-St Jeor:
  Men   = 10W + 6.25H − 5A + 5
  Women = 10W + 6.25H − 5A − 161

Katch-McArdle:
  BMR = 370 + 21.6 × lean mass (kg)
  lean mass = weight × (1 − body fat %)

Source: Mifflin et al. (1990); Katch & McArdle lean-mass equation.

How to use this calculator

  1. Enter your sex, age, height and weight.
  2. If you know your body fat percentage, add it — this unlocks the Katch-McArdle row.
  3. Compare the two results; a large gap usually means your body fat estimate is off.
  4. Multiply your BMR by 1.2 to 1.9 to get your real daily burn.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is what you burn doing absolutely nothing. TDEE is BMR plus all movement, exercise and digestion — the total you actually burn in a day. TDEE is the number your food intake should be compared against.

Should I eat below my BMR?

Generally no. Eating below BMR for extended periods makes it hard to get enough protein, fibre and micronutrients, and increases the chance of muscle loss. A modest deficit below TDEE is more sustainable.

Does building muscle raise my BMR?

Slightly. Each kilogram of muscle burns roughly 13 kcal per day at rest versus about 4.5 kcal for fat. Gaining 5 kg of muscle raises BMR by around 65 kcal — helpful, but not the metabolic furnace people imagine.

Why is my BMR lower as I get older?

Lean mass tends to decline with age while fat mass increases, and both shifts pull BMR down. Staying active and eating enough protein slows this considerably.

Related calculators

  • Calorie Calculator — Free calorie calculator using the Mifflin-St Jeor equation. See how many calories you should eat to maintain, lose or gain weight, plus your BMR.
  • Body Fat Calculator — Estimate your body fat percentage from waist, neck and hip measurements using the US Navy circumference method. Works in metric and imperial.
  • Macro Calculator — Free macro calculator. Get your daily protein, carbohydrate and fat targets in grams based on your TDEE and whether you want to lose fat, maintain or build muscle.

These figures are estimates from population formulas, not medical advice. Individual needs vary. If you are pregnant, managing a medical condition, or under 18, talk to a doctor before changing your diet.