BMR Calculator
Calculate your Basal Metabolic Rate — the calories you burn at rest.
Results update as you type.
About this calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep vital functions — breathing, circulation, cell repair — running. This BMR calculator uses the Mifflin-St Jeor equation by default and offers the Harris-Benedict and Katch-McArdle formulas as alternatives. The result is the calories you would burn doing nothing all day; multiply it by an activity factor to get the calories you actually need.
For example, a 30-year-old woman who is 165 cm and 60 kg has a BMR of about 1,320 calories under Mifflin-St Jeor — the energy her body uses purely at rest. From that the calculator suggests a weight-loss intake of 500 fewer and a weight-gain intake of 300 more calories, and lists maintenance calories for each activity level in the table below.
Use BMR as the foundation of any calorie plan, to understand your resting energy needs, and to compare how the three equations estimate them. The Katch-McArdle option is the most tailored if you know your body fat percentage, since it works from lean body mass rather than total weight.
Frequently asked questions
What is the Mifflin-St Jeor equation?
For men: BMR = 10×kg + 6.25×cm − 5×age + 5. For women the last term is −161. It is the most accurate simple BMR formula for most people.
Is BMR the same as calories I should eat?
No. BMR is your at-rest burn. To maintain weight you eat around your BMR times an activity factor (your TDEE), which is higher.
What is the difference between BMR and TDEE?
BMR is only the energy you burn at rest, whereas TDEE scales it up by how active you are. This calculator reports BMR as the headline figure and lists the matching maintenance calories for each activity level in the table beneath it.
Which BMR formula should I choose?
Mifflin-St Jeor is the current standard and works well for most people. Harris-Benedict is an older revised equation, and Katch-McArdle is best if you know your body fat percentage. Switch between them under advanced options to compare.
What is the Katch-McArdle formula?
Katch-McArdle bases BMR on lean body mass instead of total weight: 370 + 21.6 × lean mass in kilograms. Because it accounts for muscle, it is often the most accurate for lean or muscular people, but it needs your body fat percentage.
Why does my BMR drop as I get older?
Every version of the formula subtracts calories for age, reflecting the gradual loss of muscle and the slowing of metabolism over the years. That is why an older person of the same height and weight has a lower BMR than a younger one.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/bmr/curl
curl "https://calculator.free/api/v1/bmr/?sex=male&age=30&units=metric&height=175&weight=70"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/bmr/?" + new URLSearchParams({
"sex": "male",
"age": "30",
"units": "metric",
"height": "175",
"weight": "70"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.