BMR Calculator

Find your Basal Metabolic Rate — the calories your body burns at complete rest — and your total burn across activity levels.

Your Details

years
cm
kg

Your Results

Basal Metabolic Rate (BMR)
0 kcal/day
Calories burned at complete rest
0
Sedentary (x1.2)
0
Lightly Active (x1.375)
0
Moderately Active (x1.55)
0
Very Active (x1.725)
0
Extra Active (x1.9)
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What is BMR and How is it Calculated

Basal Metabolic Rate (BMR) is the number of calories your body needs for basic life-sustaining functions — breathing, circulation, cell production and organ function — while completely at rest. It typically accounts for 60-75% of the calories you burn each day.

The Mifflin-St Jeor formula

Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5

Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161

This is one of the most reliable general-population BMR formulas, because it only needs easily measured inputs — no body fat percentage or lab test required.

Why do the formulas differ by gender and age?

Men typically carry more lean muscle mass than women at the same height and weight, and muscle burns more calories at rest than fat — hence the different constants (+5 vs. −161). The −5×age term reflects that metabolic rate tends to slow with age, largely because lean muscle mass gradually declines over time unless actively maintained through strength training.

From BMR to total daily burn

BMR only measures calories burned at rest, so we multiply it by an activity factor to estimate Total Daily Energy Expenditure (TDEE) — the calories you actually burn including movement, exercise and daily activity.

Activity levelFactorTypical pattern
Sedentary×1.2Little or no exercise, desk job
Lightly Active×1.375Light exercise 1-3 days/week
Moderately Active×1.55Moderate exercise 3-5 days/week
Very Active×1.725Hard exercise 6-7 days/week
Extra Active×1.9Physical job plus daily training

How to calculate your BMR and TDEE, step by step

  1. Select your Gender and enter your Age in years.
  2. Enter your Height in centimetres and Weight in kilograms.
  3. Click Calculate BMR to see your Basal Metabolic Rate — the calories you burn at complete rest.
  4. Review the activity-level table to see your Total Daily Energy Expenditure (TDEE) from Sedentary to Extra Active.

Why this matters for calorie targets

Eating far below your BMR for extended periods can slow metabolism and cause nutrient deficiencies, since BMR represents the minimum your body needs just to function. Calorie surpluses or deficits for weight goals should generally be planned against your TDEE, not your BMR.

Disclaimer: These figures are estimates for general awareness only and not medical advice. Please consult a doctor or registered dietitian for personalised guidance.

Frequently Asked Questions

Men typically carry a higher proportion of lean muscle mass than women at the same height and weight, and muscle burns more calories at rest than fat tissue. The Mifflin-St Jeor equation accounts for this with a +5 constant for men versus a -161 constant for women, so two people with identical height, weight and age get different BMR estimates based on this average physiological difference.

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest, just to stay alive. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor, representing the calories you actually burn in a day including movement, exercise and daily activity. TDEE is always higher than BMR, and is the more useful number for setting calorie targets.

The formula subtracts 5 × age, reflecting that metabolic rate tends to slow with age — largely due to a gradual loss of lean muscle mass over time, which burns more calories at rest than fat. This is also why maintaining muscle mass through strength training becomes more relevant for metabolism as people get older.

Eating below your BMR for extended periods can be counterproductive and potentially harmful, since your BMR represents the minimum calories your body needs just to keep vital functions running. Sustained deficits below BMR can slow metabolism, cause nutrient deficiencies, and lead to muscle loss rather than fat loss — calorie deficits for weight loss are generally planned against TDEE, not BMR.

The Mifflin-St Jeor equation was designed to be usable with easily measured inputs — weight, height, age and gender — without requiring specialized body composition testing. Formulas that directly use lean body mass (like the Katch-McArdle equation) can be more accurate for people with atypical muscle-to-fat ratios, but need a body fat percentage measurement most people don't have on hand.

Choose based on your typical week, not your best day: Sedentary means little to no exercise and a desk job; Lightly Active means light exercise 1-3 days a week; Moderately Active means moderate exercise 3-5 days a week; Very Active means hard exercise 6-7 days a week; Extra Active means a physically demanding job plus daily training. Most people overestimate their activity level, so when unsure, pick the lower option.

It doesn't account for individual differences in muscle mass, genetics, hormonal conditions (like thyroid disorders), sleep quality, or medications, all of which can shift actual metabolic rate above or below the formula's estimate. These figures are estimates for general awareness only and not medical advice — consult a doctor or registered dietitian for personalised guidance.
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