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.

A worked example, step by step

Take the default inputs — a 30-year-old man, 170 cm, 70 kg, moderately active. The Mifflin-St Jeor equation gives a BMR of (10×70) + (6.25×170) − (5×30) + 5 = 700 + 1,062.5 − 150 + 5, which is about 1,618 calories a day at complete rest. Multiplying by the moderate-activity factor of 1.55 yields a TDEE of roughly 2,508 calories — the maintenance figure. A mild 500-calorie deficit for gradual loss lands near 2,000 a day; a 250-calorie surplus for slow gain lands near 2,750.

Change one input and watch how much the answer moves. Switch the same person to "sedentary" (factor 1.2) and TDEE drops to about 1,940 — a difference of nearly 570 calories a day purely from the activity setting. That single dropdown moves the result more than almost any other input, which is exactly why honest activity self-assessment matters so much: pick the level above your real one and you'll wonder why a "deficit" isn't producing any loss.

Why the scale doesn't always agree with the math

People often expect a 500-calorie daily deficit to produce a clean half-kilogram of loss every week, then get discouraged when week three shows nothing. Several ordinary things break the tidy arithmetic. Water weight swings daily by more than the fat you're losing, easily masking real progress on any given morning. Metabolic adaptation means TDEE drifts down as you lose weight — a lighter body burns fewer calories, so the deficit you started with shrinks over time. And logging error is larger than most people believe; studies consistently find people underestimate intake by a meaningful margin. None of these mean the formula failed. They mean the estimate is a starting point you calibrate against the scale over two to four weeks, adjusting by 100–200 calories, rather than a promise to be met on day seven.

Turning the number into a plan

A TDEE figure is only useful once it connects to the rest of your day. Use the ideal weight calculator to set a sensible target-weight range, then let this tool tell you the daily calories to reach it. The steps-to-calories tool shows how much daily movement contributes to the "activity" side of the equation — often less than people assume, which is why diet usually drives weight change more than exercise. For the reasoning behind gradual, sustainable deficits over crash approaches, our steps and calories guide puts the energy-balance picture together. Read on every result here: these are educational estimates, and a registered dietitian can turn them into a plan that fits your health and life.

Frequently asked questions