BMR Calculator

BMR = 10 × weight + 6.25 × height − 5 × age + s (s = +5 in men, −161 in women)

weight

Body weight in kilograms (kg)

height

Height in centimetres (cm)

age

Age in whole years

s

Sex constant: plus 5 for men, minus 161 for women

Reach for it when you want a resting metabolic rate baseline to build a calorie target on. If you know your body fat percentage, Katch-McArdle fits better because it works from lean mass; if you want the calories that hold your current weight, start from TDEE instead.

1. A 30-year-old man, 175 cm and 70 kg

   1. Weight term: 10 × 70 = 700
   2. Height term: 6.25 × 175 = 1093.75
   3. Age term: 5 × 30 = 150, subtracted
   4. Add the male constant: 700 + 1093.75 − 150 + 5 = 1648.75 kcal/day
   5. In kilojoules: 1648.75 × 4.184 = 6898 kJ

   The same body with the female constant lands 166 kcal lower, because the two constants differ by exactly that much.

2. A 100-year-old woman, 175 cm and 70 kg

   1. Weight and height terms: 700 + 1093.75 = 1793.75
   2. Age term: 5 × 100 = 500, subtracted
   3. Female constant: −161
   4. 1793.75 − 500 − 161 = 1132.75 kcal/day
   5. Per hour: 1132.75 ÷ 24 = 47.2 kcal

   Seventy years of ageing costs 516 kcal a day here, about a third of the total — which is why the age field is not optional.

BMR is not a calorie target. It is what you burn lying still, before any movement, digestion or exercise, and real daily needs run 20 to 50 percent higher once activity is added. The equation also assumes a healthy adult of average build: it reads low for trained athletes and for very tall people. It does not use body fat, so a 90 kg lifter and a 90 kg sedentary adult get the same figure. Pregnancy, burns, fever and thyroid disease all move resting expenditure away from the prediction.

What is a BMR calculator?

A BMR calculator estimates the energy your body needs at complete rest, in kilocalories per day. It works from your sex, age, height and weight and ignores activity, exercise and digestion entirely. Multiply the result by an activity factor to reach the calories that hold your weight steady.

Which formula does this BMR calculator use?

It uses the Mifflin-St Jeor equation, published in 1990 and recommended by the Academy of Nutrition and Dietetics for healthy adults. The older Harris-Benedict equation from 1919 overestimates resting needs for most people by roughly 5 to 15 percent, which is why it is not offered here.

What is the difference between BMR and TDEE?

BMR is the resting floor; TDEE, total daily energy expenditure, adds movement, work and exercise on top of it. The gap is large: a desk worker who never trains lands near 1.2 times BMR, while someone in a physical job who trains daily can reach 1.9 times.

Why is my BMR different from the number another site gives me?

Every equation is a population average, so two people of the same height and weight can differ by 10 percent or more. Mifflin-St Jeor carries a margin of roughly plus or minus 10 percent for healthy adults, and measuring resting expenditure in a lab is the only way to narrow that down.

Should I eat at my BMR to lose weight?

No — it is the floor, not a target. Eating at BMR leaves nothing for the energy you spend moving, and intakes below about 1,200 kilocalories a day are hard to keep nutritionally complete. Set the target from TDEE minus a moderate deficit instead.

• A new predictive equation for resting energy expenditure in healthy individuals — Mifflin MD, St Jeor ST, et al. — American Journal of Clinical Nutrition, 1990
• Human energy requirements: report of a joint FAO/WHO/UNU expert consultation — Food and Agriculture Organization of the United Nations