How many calories do you need?
The calculator first estimates your basal metabolic rate (BMR), the energy your body uses at complete rest, and then multiplies it by your activity level. The result is the number of Calories that keeps your weight stable. Eating less than that makes you lose weight; eating more makes you gain.
Example: a 25-year-old man, 5 ft 10 in and 160 lb, who exercises 4 to 5 times a week has a BMR of about 1,717 Calories with the Mifflin-St Jeor formula and needs about 2,515 Calories a day to keep his weight.
Calories and weight change
A pound of body fat holds roughly 3,500 Calories, so eating 500 Calories a day below your maintenance level leads to a loss of about 1 lb a week. The body adapts over time, so progress usually slows; recalculate as your weight changes.
Which formula to use
- Mifflin-St Jeor: the most accurate for most people and the default here.
- Revised Harris-Benedict: an older formula that gives slightly higher numbers.
- Katch-McArdle: based on lean body mass, so it suits lean, muscular people who know their body fat.
Frequently asked questions
Are calorie needs exact?
No. The formulas estimate the average for people like you; real needs can differ by 10% or more. Track your weight for a few weeks and adjust.
Do all calories count the same?
For weight, mostly yes. For health, the source matters: protein, fiber and whole foods keep you full and support muscle better than sugary drinks and snacks.
What is a Calorie?
Food energy is measured in kilocalories, written Calories with a capital C. One Calorie is about 4.184 kilojoules.