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Resting Metabolic Rate (Mifflin) Calculator

Estimate calories burned at rest with Mifflin-St Jeor

How it is calculated

Resting metabolic rate is the energy your body uses at complete rest. The Mifflin-St Jeor equation estimates it as base = 10 × weight + 6.25 × height − 5 × age, with weight in kg, height in cm and age in years. Then 5 is added for men and 161 is subtracted for women: RMR = base + 5 (male) or RMR = base − 161 (female). The answer is in kilocalories per day, rounded to a whole number. All three numbers must be above zero. This is a population-average estimate; it ignores muscle mass, so a very muscular or very lean person may differ. It does not include activity.

Worked example

A 30-year-old man, 70 kg, 175 cm. Base: 10 × 70 = 700, plus 6.25 × 175 = 1093.75, minus 5 × 30 = 150, giving 1643.75. Add 5 for men: 1648.75. Rounded, the estimate is 1,649 kcal/day at rest. Daily energy needs are higher once movement is counted.

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Common mistakes

  • Entering weight in pounds or height in inches or feet. The equation expects kilograms and centimetres.
  • Treating RMR as the number of calories to eat. It excludes daily activity, so total needs are higher.
  • Choosing the wrong sex, which shifts the result by 166 kcal, the gap between +5 and −161.
  • Expecting the value to match a lab test exactly. The equation estimates an average, and muscle mass and other factors cause real differences.
  • Using a very low RMR as a calorie target for dieting without medical guidance.

About this calculator

This calculator uses the Mifflin-St Jeor equation, published in 1990 and now the formula most dietitians consider the most accurate for estimating resting metabolic rate in the general population: for men, RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women, the same terms minus 161 instead of plus 5. It replaced the older Harris-Benedict equation after studies showed it more closely matched measured energy expenditure, especially in people with overweight or obesity.

Dietitians and fitness coaches use the result as the baseline for a calorie target: multiplying RMR by an activity factor gives total daily energy expenditure, from which a calorie deficit or surplus is planned for weight loss or muscle gain.

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