An honest estimate of what you burn, and a gentle target if you want to lose weight.
The equation behind the number
Your resting burn is the Mifflin-St Jeor equation, which has been the default in dietetic practice since it outperformed the older Harris-Benedict formula in validation work. It is 10 times your weight in kilograms, plus 6.25 times your height in centimetres, minus 5 times your age, plus 5 for men or minus 161 for women.
That resting figure is then multiplied by how much you move: 1.2 for a desk day, 1.375 for light activity, 1.55 for moderate and 1.725 for hard training.
The part worth knowing. The equation is fitted to population averages, and individual resting burn varies by roughly 200 to 300 calories either side of what any formula predicts, mostly from differences in lean mass. The activity multiplier is cruder still, because it asks you to sort your whole week into one of four boxes. Use the number as a starting point and let two or three weeks of actual weight change correct it, which is the only calibration that is about you.
Every figure on this site names where it came from. How we check.
If you are buying a scale
Any consistent scale works if you weigh at the same time each morning. Smart scales that log the trend automatically make the habit stick, and the trend matters more than any single day.
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Common questions
How many calories a day does an adult need?
Most adult women need roughly 1,800 to 2,200 calories a day and most adult men need roughly 2,200 to 2,800, depending on size and activity. A small, mostly sedentary older adult may need less, and a tall, active person may need more. This calculator gives you a personal estimate rather than a one-size number.
Why do crash diets fail?
When you cut calories very hard, your body fights back: it slows its energy use, a change called metabolic adaptation, and it burns muscle along with fat. Hunger hormones also rise, so most people regain the weight, sometimes plus extra, once the diet ends. Slow, steady changes keep more muscle and are far easier to hold onto.
How big a calorie deficit should I use to lose weight?
A deficit of about 400 to 500 calories a day below your maintenance number leads to roughly one pound of loss per week for most people. That pace is slow enough to protect muscle and gentle enough to live with. If you take medications or have health conditions such as diabetes, plan any weight loss with your own doctor.
Does metabolism really slow down with age?
Less than most people believe. Recent large studies found that calorie burn per unit of body tissue is quite stable from about age 20 to 60, with a clear decline only after 60. What changes for most people in midlife is less muscle and less daily movement, both of which you can act on with strength exercise and walking.
How many calories should I eat to lose weight?
About 500 below your maintenance number is the standard, sustainable deficit, which produces roughly half a kilogram, or one pound, a week. Steeper cuts backfire for most people: hunger wins, muscle goes with the fat, and the weight returns. Calculate your maintenance above, subtract 500, and hold it for a month before judging.