BMR Calculator formula — how it actually works
The whole calculator is one formula: Men (Mifflin-St Jeor): BMR = 10 × weight + 6.25 × height − 5 × age + 5; women use − 161 instead of + 5. Every field on the page feeds exactly one part of that formula, and nothing else is going on behind the scenes. Knowing that makes the result checkable, not mysterious.
Worked example: A 30-year-old man, 70 kg, 175 cm: BMR = 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,649 kcal a day. You can follow that example by hand with a pocket calculator. If your hand calculation gives a different answer, compare each input one by one — the formula rarely goes wrong, but a mistyped input goes wrong often.
A useful hand check is to try a round-number version first. Round numbers make the arithmetic easy to follow, and they confirm you understand the method before you trust it with your real figures. Once the method checks out, the real figures are just a second run.
One limit of the formula: BMR is the energy your body uses at rest. Daily needs are higher, because activity is added on top — BMR alone is not a calorie target. The formula is correct for what it covers, and silent about what it does not. Read the result with that limit in mind.
Frequently asked questions
What does each symbol in the formula mean?
Each symbol is one field on the tool page, in the same order. The formula page on the tool itself names them, and the worked example shows them substituted with real numbers.
Can I check the result by hand?
Yes, and you should try it once with round numbers. The worked example on the tool page is designed to be checkable with a pocket calculator.
Does the formula include tax, fees or other charges?
Only what the formula says. Anything outside it — tax, fees, charges, or real-world variation — sits outside the result, so read the result with that in mind.
More guides on the BMR Calculator
- How to use the BMR Calculator — step by step
- BMR Calculator explained with worked examples
- BMR Calculator for beginners — start here
- Common mistakes people make with the BMR Calculator
- BMR Calculator vs doing it by hand — which is faster?
- bmr calculator — the complete guide
- How to get an accurate result from the BMR Calculator
- BMR Calculator for students — with examples
- BMR Calculator for homeowners and DIYers
Enter your age, weight, height and sex to see your basal metabolic rate in calories a day.