Daily calorie calculator.

How your daily calorie number is built

This calculator estimates your total daily energy expenditure (TDEE), the calories you burn in a typical day, in two steps. First it estimates your basal metabolic rate (BMR), the energy your body uses at rest, with the Mifflin-St Jeor equation. Then it multiplies that figure by an activity factor to cover everything you do beyond lying still.

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
• TDEE = BMR × activity factor (1.2 sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active, 1.9 extra active)

Mifflin and colleagues derived the equation from 498 healthy adults aged 19 to 78 whose resting energy expenditure had been measured by indirect calorimetry. In that sample the older Harris-Benedict equations, published in 1919, overestimated measured resting expenditure by about 5%. A later systematic review of predictive equations found Mifflin-St Jeor the most likely of those it tested to land within 10% of a measured value, while warning that errors for any one person can still be sizeable.

The activity factors are conventions, not measurements. They are a quick way to express how much energy movement adds on top of resting needs, which is why two calculators using different factors can disagree by a few hundred calories for the same person.

Worked example

A 35-year-old woman, 165 cm and 62 kg, who exercises one to three days a week (lightly active):

1. BMR = 10 × 62 + 6.25 × 165 − 5 × 35 − 161 = 620 + 1,031.25 − 175 − 161 = 1,315 kcal
2. TDEE = 1,315.25 × 1.375 = 1,809 kcal per day (the maintenance estimate)
3. The planning targets on the calculator are percentages of that figure: −10% is about 1,628, −20% is about 1,447, +10% is about 1,990 and +20% is about 2,171 kcal.

If you have a good estimate of your fat-free mass, the same Mifflin paper also reports a fat-free-mass equation: resting expenditure = 19.7 × fat-free mass (kg) + 413. People with unusually high or low muscle mass can be mis-estimated by the weight-based equation, so that version is worth comparing if you know your body composition (see the body fat calculator).

Choosing an activity level honestly

The most common mistake is picking too high a level. The factor describes your whole week, not your best training day. A desk job with three gym sessions is usually closer to "lightly active" than "very active". If you are between two levels, start with the lower one, track your weight and intake for two to three weeks, and adjust. Real-world feedback beats any formula.

Using the number for weight change

Maintenance calories are a starting estimate, not a promise. Rules such as "3,500 calories equals one pound" treat the body as a fixed bank account, but metabolism adapts. In a 2011 Lancet analysis, Hall and colleagues showed that bodyweight responds slowly to a change in intake, with half times of about a year, and that accurate prediction needs a dynamic model instead of a fixed rule. In practice, recalculate as your weight changes and judge the plan by two or three weeks of trend, not a single day. The NIDDK offers a free Body Weight Planner if you want to estimate the calories needed to reach a goal weight by a chosen date.

What this calculator does not cover

• Pregnancy, breastfeeding, children and teenagers, who have different needs.
• Medical conditions, medications, or eating disorders. Talk to a doctor or registered dietitian.
• Macronutrient targets. Use the macro calculator or the protein intake calculator for the split.
• Calories burned in a specific workout. See the calories burned calculator.

Canadian users: the maths is the same everywhere. The calculator takes centimetres and kilograms, so convert from feet and pounds first (1 in = 2.54 cm; 1 lb = 0.4536 kg).