Calorie calculator

What are maintenance calories?

Maintenance calories are roughly how many calories your body uses in a typical day: the energy it burns at rest, plus what you burn moving around and exercising. Eating about that amount tends to keep your weight steady. It is an estimate, and your real number can be higher or lower.

How this calculator works

It first estimates the energy your body uses at rest, called your basal metabolic rate (BMR), with the Mifflin-St Jeor equation, a widely used formula based on sex, age, height, and weight. It then multiplies that by an activity factor, from 1.2 for mostly sitting up to 1.9 for very hard daily exercise or a physical job, to estimate what you use across a full day. Results are rounded to the nearest 10 calories.

What about losing weight?

A gradual approach is generally recommended. Harvard Health notes that eating at least 500 fewer calories a day, together with regular physical activity, is a common way to aim for losing about a pound a week, and that daily intake should not fall below 1,200 calories for women or 1,500 for men except under the supervision of a health professional. This calculator never shows a weight-loss estimate below those levels. Weight change is not perfectly predictable, so for a more personalized picture, the NIH Body Weight Planner models how weight may change over time.

What an estimate can't tell you

Any formula describes an average. Two people with the same numbers can burn noticeably different amounts depending on muscle mass, genetics, sleep, hormones, some medical conditions, and some medications. Activity levels are also easy to over- or underestimate. Treat the result as a starting point, watch how your weight actually responds over a few weeks, and adjust with a professional's help. It is not designed for pregnancy, breastfeeding, children and teens, or anyone managing a condition that affects eating or weight.

Common questions

Why does the calculator ask which formula to use?

The Mifflin-St Jeor equation comes in two versions, one for each sex, because average body composition differs. If neither fits your situation, for example if you take gender-affirming hormones, a provider can help you interpret the result.

How accurate is it?

It is a reasonable starting estimate for many adults, but individual needs can differ noticeably from any formula. Your actual weight trend over a few weeks is a reliable real-world check.

Should I eat this many calories?

Not necessarily. The number estimates what keeps your weight steady. Whether you should eat more, less, or the same depends on your goals and your health, which is a conversation to have with a licensed provider or a registered dietitian.

Can I use it during pregnancy?

No. Calorie needs change during pregnancy and breastfeeding, and this calculator does not account for that. Your prenatal care provider can advise.