Estimates how many calories you burn in a day, and what to eat to hold, lose, or gain weight.
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Sex
Most people sit one level lower than they think.
Calories a day to maintain
2,295
Your estimated total daily energy expenditure
About 0.5 kg a week
About 0.25 kg a week
A modest surplus
Burned doing nothing at all
The resting rate is the reliable half of this. The activity multiplier is a guess, so treat the daily totals as a starting point and adjust after two or three weeks of watching your weight.
Basal metabolic rate is what your body burns doing nothing at all: keeping you warm, breathing, running a brain. It is roughly 60 to 70 percent of most people's daily total.
Total daily energy expenditure is BMR multiplied by an activity factor, and it is the number you actually eat against. This tool shows both, because the gap between them is where the activity multiplier does its guessing.
Mifflin-St Jeor, which is the equation most dietitians reach for and generally more accurate for modern populations than the older Harris-Benedict. It takes weight, height, age, and sex.
It does not take body composition, which is its main weakness. Two people of identical height, weight, and age get identical estimates even if one carries far more muscle. If you know your body fat percentage, the Katch-McArdle formula will serve you better.
The BMR part is reasonably well established. The activity factor is a blunt instrument, and it is where most of the error lives. People routinely overestimate how active they are, and the gap between "moderately active" and "very active" is several hundred calories.
Treat the output as a starting point rather than a measurement. Eat at the estimate for two or three weeks, track your weight, and adjust from what actually happens. Your own data beats any equation within a month.
A deficit of about 500 calories a day works out near half a kilogram a week, which is the usual recommendation because it is aggressive enough to see and mild enough to sustain. Larger deficits cost you more muscle and get abandoned more often.
Gaining is slower. A surplus of 250 to 500 calories a day supports muscle gain without much fat coming along for the ride. Going harder mostly adds fat.
Sex, age, height, and weight. These feed the Mifflin-St Jeor equation for your basal rate.
Most people sit one level lower than they think. Desk job with three gym sessions a week is lightly to moderately active, not very active.
That is the figure to eat at if you want to stay where you are. Loss and gain targets are derived from it.
Eat at the estimate for two to three weeks and watch your weight trend. Adjust by 100 to 200 calories based on what happened, not what the formula said.
Enter height and weight. The number appears as you type, and nothing leaves your browser.
A weight-based estimate of daily fluid, adjusted for exercise and heat.
The US Navy circumference method. All you need is a tape measure.
A calculator tells you where you are once. If the thing you actually want is to keep something up, that takes a record rather than a result.
