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BMR Calculator (Basal Metabolic Rate)

From age, height, weight and activity level: your BMR and total daily energy expenditure.

How it is calculated

Basal metabolic rate (BMR) is estimated with the Mifflin–St Jeor equation: BMR = 10 × weight + 6.25 × height − 5 × age + s, with weight in kg, height in cm, age in years, and s = +5 for men or −161 for women. Total daily energy expenditure is TDEE = BMR × activity factor, where the factor (for example 1.2 for a desk-bound day, higher for training) describes how active you are. Results are rounded to whole kcal per day. Age is cut to whole years. The equation is an estimate for adults; real needs vary with muscle mass and other factors.

Worked example

A 45-year-old woman, 62 kg, 165 cm, activity factor 1.375 (light exercise 1–3 days a week). BMR = 10 × 62 + 6.25 × 165 − 5 × 45 − 161 = 620 + 1,031.25 − 225 − 161 = 1,265.25, shown as 1,265 kcal/day, roughly what her body uses at complete rest. TDEE = 1,265.25 × 1.375 ≈ 1,740 kcal/day, which is roughly the intake that keeps her weight stable.

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Common mistakes

  • Entering weight in pounds or height in inches or metres; the equation needs kg and cm.
  • Treating BMR as the calorie target; you also need the activity factor to get the daily total.
  • Choosing an activity factor that is too high; most people overestimate their activity level.
  • Applying the male constant to a woman, which shifts the result by 166 kcal.

Sources

About this calculator

Basal Metabolic Rate estimates how many calories a body would burn in a day doing nothing but the essential work of staying alive, such as breathing, circulating blood, and maintaining organ function. The calculation typically draws on established formulas that combine weight, height, age, and sex to approximate this resting energy baseline, since it can't be measured directly without lab equipment.

It's a starting point for anyone building a nutrition or fitness plan, because every other calorie estimate, like how much someone burns with daily activity added on top, builds on this baseline number. People trying to lose, gain, or maintain weight typically calculate it first before layering activity level on top.

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Comments (1)

  • Editorial team

    Take a 30 year old man, 80 kg and 180 cm: the equation gives 1,780 kcal a day, and with an activity factor of 1.55 the total is 2,759 kcal. Treat the total as a starting estimate rather than a target, and compare it with how your weight actually moves over a few weeks. The factor is entirely your own judgement, so be honest about it. Which activity factor do you use, and how did you choose it?

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