Calorie Calculator

Calculate daily calorie needs using the Mifflin-St Jeor equation

What is it and how does it work?

A calorie calculator estimates how many calories your body needs in a day, based on your age, sex, height, weight and activity level. It works in two steps: first it calculates your basal metabolic rate (BMR) — the energy you burn at rest just to keep your body running — using the Mifflin-St Jeor equation, the formula most dietitians consider the most accurate. Then it multiplies that by an activity factor to estimate your total daily energy expenditure (TDEE), the calories you actually use across a normal day.

That TDEE number is the anchor for any goal: eat roughly that amount to maintain your weight, fewer to lose, more to gain. Seeing it makes nutrition concrete rather than guesswork, because it turns "eat less" into an actual target you can build meals around. It is worth being clear that this is an estimate from a population formula, not a personalised medical figure — real needs vary with body composition, genetics and health conditions. This tool calculates everything in your browser, so the details you enter stay on your device.

Common use cases

• Setting a weight goal: find your maintenance calories, then adjust up or down to plan gaining or losing weight.
• Planning meals: use your daily target as a budget to structure portions across the day.
• Understanding activity's effect: see how a more active lifestyle raises the calories you can eat at maintenance.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy your body uses at complete rest just to stay alive. TDEE is BMR multiplied by an activity factor to account for movement, exercise and daily life — so TDEE is always higher and is the number that reflects what you actually burn.

Why the Mifflin-St Jeor equation?

It is the formula most widely recommended by dietitians because studies found it estimates resting metabolic rate more accurately than older equations for most people. It uses age, sex, height and weight, which is why all four affect the result.

How accurate is the estimate?

It is a solid starting point but an estimate, not a precise measurement. Real needs vary with muscle mass, genetics, hormones and health, so use the number as a baseline and adjust based on how your weight actually responds over a few weeks.

Is this medical or nutritional advice?

No. It is an informational estimate from a general formula, not personalised medical guidance. For health conditions, significant weight goals or a medical diet, consult a doctor or registered dietitian who can account for your individual situation.

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