TDEE Calculator

The Mifflin-St Jeor equation in full

For men, BMR is 10 times your weight in kilograms, plus 6.25 times your height in centimeters, minus 5 times your age, plus 5. For women it is the same three terms with 161 subtracted instead of 5 added. The equation is written in metric, so pounds and feet get converted before any of that happens. What it hands back is only the cost of keeping you alive at rest, which is why BMR always looks alarmingly low next to what you actually eat in a day. Everything you do on top of lying still, walking to the car included, is what the activity number is standing in for.

A worked example

Take a 30 year old man who weighs 80 kilograms and stands 178 centimeters tall. His BMR is 10 times 80, which is 800, plus 6.25 times 178, which is 1,112.5, minus 5 times 30, which is 150, plus 5. Add that up and BMR lands at about 1,768 calories a day just to run his body at rest. If his week is a mix of a desk job and workouts 3 to 5 days, that is moderately active, a 1.55 multiplier. Multiply 1,768 by 1.55 and his TDEE comes out to roughly 2,740 calories a day, the number he would eat around to hold his weight steady.

The activity multipliers

• Sedentary, little or no exercise: about 1.2
• Lightly active, 1 to 3 days a week: about 1.375
• Moderately active, 3 to 5 days a week: about 1.55
• Very active, 6 to 7 days a week: about 1.725
• Extra active, athlete or physically demanding job: about 1.9

Picking one level too high is the single most common reason a TDEE number stops matching reality, so when in doubt round down.

Why it is an estimate

Mifflin-St Jeor is the most accurate formula we have for predicting BMR from a few basic measurements, but it is still a population average: two people with identical height, weight, age, and sex can genuinely need different numbers. The activity level is self-reported on top of that, and almost everyone remembers their busy weeks more vividly than their quiet ones. So let your weight trend over 2 to 3 weeks be the tiebreaker. If the scale is not doing what the number predicted, it is the number that is wrong, not you.

What to do with your number

TDEE is the anchor every other nutrition decision gets made against. Once you have it, use it to set your calorie deficit if the goal is losing fat, or to plan a surplus if the goal is gaining. From there, your macros split that calorie target into protein, carbs, and fat so the plan is something you can actually eat, not just a number on a screen. If you want to see the whole thing worked through with real numbers before you commit to a target, I walked one out in how many calories to maintain your weight.