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BMR calculator (Mifflin-St Jeor)

Basal metabolic rate is what you burn doing nothing at all. Mifflin-St Jeor, published in 1990, replaced Harris-Benedict as the default because it fits modern populations better.

years
Basal metabolic rate
1649kcal/day
= Exact BMR (Mifflin-St Jeor)
Daily energy needs at that activity level
2267 kcal/day
For roughly 0.45 kg a week of loss
1767 kcal/day
For a slow gain
2567 kcal/day
BMR in kilojoules
6898 kJ/day
Show the working
  1. Weight = 70
  2. Height = 175
  3. Age = 30
  4. Sex = 1
  5. Activity level = 1.375
  6. Basal metabolic rate = 10*70 + 6.25*175 - 5*30 + (1 > 0 ? 5 : -161) = 1648.75
  7. Daily energy needs at that activity level = 1648.75 * 1.375 = 2267.03
  8. For roughly 0.45 kg a week of loss = 2267.03 - 500 = 1767.03
  9. For a slow gain = 2267.03 + 300 = 2567.03
  10. BMR in kilojoules = 1648.75 * 4.184 = 6898.37

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • Men: BMR = 10 W + 6.25 H - 5 A + 5
    • Women: BMR = 10 W + 6.25 H - 5 A - 161
    • W in kg, H in cm, A in years. TDEE = BMR x activity factor.

    The standard error is around 10%, so two people with identical inputs can genuinely differ by 200 kcal a day.

    A deficit of 500 kcal a day is the traditional half-kilo-a-week rule. It overstates long-run loss, because metabolic rate falls as you do.

    This is a population formula, not a diagnosis. Individual metabolism, body composition and medical history all move the real answer, so treat the number as a starting point and talk to a clinician about anything that matters.

    Frequently asked

    Which BMR formula is most accurate?

    Mifflin-St Jeor for people of normal body composition. Katch-McArdle is better if you know your body fat percentage, because it works from lean mass.

    What is the difference between BMR and TDEE?

    BMR is at complete rest. TDEE multiplies it by an activity factor to cover everything else you do in a day.

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