BMR calculator
Find your Basal Metabolic Rate, the calories your body burns at rest, from your height, weight, age and sex using the Mifflin-St Jeor equation.
How it works
Your BMR is the calories your body needs at complete rest to run its basic functions, which is the biggest single slice of daily energy use. The tool uses the Mifflin-St Jeor equation, chosen because it tracks measured resting energy well for most healthy adults. The sum is ten times your weight in kilograms, plus 6.25 times your height in centimetres, minus five times your age in years. Men add five to the total and women subtract 161, which reflects the average difference in body composition.
BMR on its own does not tell you how much to eat, because it excludes all movement. To get there, multiply BMR by an activity factor: about 1.2 for a mostly still day, 1.55 for someone moderately active, and up to 1.9 for hard daily training. The result is your Total Daily Energy Expenditure, the number a maintenance or weight-change plan is built around. Knowing the resting baseline separately is useful, because it shows how much of your intake is simply keeping the body functioning.
Worked example
Take a 30-year-old woman, 165 cm tall and 65 kg. The sum is (10 x 65) plus (6.25 x 165) minus (5 x 30) minus 161, which is 650 plus 1,031 minus 150 minus 161, giving a BMR of about 1,370 kcal a day. On a fairly sedentary day that points to roughly 1,644 kcal to maintain, rising to about 2,124 kcal if she is moderately active through the week.
Common questions
What is BMR?
Basal Metabolic Rate is the number of calories your body uses at complete rest just to keep you alive: breathing, circulation, keeping warm and repairing cells. It is the largest single part of the calories you burn each day, before any movement is added.
How is BMR calculated?
This tool uses the Mifflin-St Jeor equation. For men it is ten times weight in kilograms, plus 6.25 times height in centimetres, minus five times age, plus five. For women the last term is minus 161. It is one of the more accurate simple equations for healthy adults.
What is the difference between BMR and TDEE?
BMR is what you burn at rest. Total Daily Energy Expenditure, or TDEE, is BMR multiplied by an activity factor to include everyday movement and exercise. TDEE is the figure to use when planning how much to eat; BMR is the resting baseline it is built on.
Why does BMR fall with age?
Muscle is more metabolically active than fat, and people tend to lose muscle and gain fat as they get older, so resting energy use drifts down. Staying active and keeping muscle through resistance exercise slows that decline.
Should I ever eat below my BMR?
Eating below BMR for long stretches is not recommended without medical supervision, because it can leave you short of nutrients and is hard to sustain. For weight loss, base a modest deficit on your TDEE, not your BMR.