Quick answer: With Mifflin–St Jeor, a 30-year-old man of 70 kg and 170 cm has a BMR of 10 × 70 + 6.25 × 170 − 5 × 30 + 5 = 1,618 kcal a day.
How it's calculated
Mifflin–St Jeor (1990): BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. In studies it predicts measured resting energy within 10% for most adults and is the default here.
Harris–Benedict, revised by Roza and Shizgal (1984): men 88.362 + 13.397W + 4.799H − 5.677A; women 447.593 + 9.247W + 3.098H − 4.330A. Katch–McArdle uses lean body mass only: 370 + 21.6 × lean mass (kg), so it needs your body fat percentage and suits people who know it.
All three are averages from groups of people. Muscle mass, thyroid function, medicines and illness move real BMR up or down, and only indirect calorimetry measures it. Use the result as a starting point and adjust by how your weight actually changes over a few weeks. To get daily needs, see the TDEE calculator.
Worked examples
- Man, 30, 70 kg, 170 cm (Mifflin): 700 + 1,062.5 − 150 + 5 = 1,618 kcal
- Woman, 35, 60 kg, 165 cm (Mifflin): 600 + 1,031.25 − 175 − 161 = 1,295 kcal
- 70 kg at 18% body fat (Katch–McArdle): 370 + 21.6 × 57.4 = 1,610 kcal
Frequently asked questions
What is the difference between BMR and RMR?
BMR is measured under strict conditions (fasting, fully rested, after sleep); resting metabolic rate (RMR) is measured more loosely and is usually a little higher. The formulas here are often used for both.
Which BMR formula should I use?
Mifflin–St Jeor is the one most dietitians use for healthy adults. If you know your body fat percentage reliably, Katch–McArdle can fit muscular people better.
Does BMR drop with age?
Yes, by a few kcal a year in the formulas, mostly because lean mass tends to fall. Strength training helps keep it.
Should I eat less than my BMR to lose weight?
Weight loss plans are usually built from total daily energy (TDEE), not BMR. BMR is the energy for basic body functions.
How is BMR different from TDEE?
BMR is the energy you would use at complete rest. TDEE adds your daily movement and exercise, so it is BMR multiplied by an activity factor of 1.2 to 1.9.
Does building muscle raise my BMR?
Yes, modestly, because lean tissue uses more energy at rest than fat. The Katch–McArdle option reflects this, since it works from your lean mass using your body fat percentage.