Calorie Calculator (TDEE & BMR)

What this calculator does & how it works

This tool estimates how many calories your body uses in a day so you can plan meals around a goal. It works in two steps. First it calculates your basal metabolic rate (BMR) — the energy you would burn if you did nothing but rest for 24 hours — using the Mifflin-St Jeor equation, published in 1990 and widely regarded as one of the most accurate predictive formulas for healthy adults. For men the equation is BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; for women the final constant is −161 instead of +5.

Second, it multiplies your BMR by an activity multiplier ranging from 1.2 (sedentary) up to 1.9 (extra active) to estimate your total daily energy expenditure (TDEE) — the calories you actually burn on a typical day once movement, exercise, and the work of digesting food are included. From your TDEE the calculator then derives target intakes: maintenance equals your TDEE, a mild deficit subtracts about 250 calories a day, a larger deficit subtracts about 500, and a surplus adds about 250 for gradual gain. If you enter imperial units, pounds and feet/inches are converted to metric first, so the result is the same either way.

How to interpret your results

Your maintenance number is the anchor: eat roughly that many calories and your weight should stay about the same over time. To lose weight gradually, aim a few hundred calories below it; to gain, aim a little above. A deficit of around 500 calories a day corresponds very roughly to half a kilogram (about one pound) of change per week, but this is an average, not a guarantee, and the body adapts as you go.

Treat the activity multiplier honestly — most people overestimate how active they are, which inflates the TDEE. If your weight is not moving the way the numbers predict after two or three weeks, adjust your intake by 100 to 200 calories rather than assuming the formula is "wrong." Pair this with your BMI for a sense of weight category and your water needs to round out a daily plan.

Limitations and when to consult a professional

Predictive equations estimate population averages. They do not measure your metabolism directly and can be off by several hundred calories for any one person, especially if you have a lot of muscle, very low or very high body fat, a thyroid or metabolic condition, or are very tall or very short. The equation is validated for healthy adults and is not appropriate for children, during pregnancy or breastfeeding, or for people with eating disorders, where calorie counting can be harmful.

Use these figures as a starting estimate, not a rule. If you are managing a medical condition, taking medication that affects weight, recovering from an eating disorder, or simply unsure how to set a safe target, speak with a doctor or a registered dietitian. They can tailor a plan to your full health picture in a way a calculator cannot. Nothing here is medical advice.

Frequently asked questions