Calorie Calculator

Where the number comes from

Your body burns calories in three ways: keeping you alive at rest, digesting food, and moving. The calculator estimates the first with the Mifflin-St Jeor equation, then multiplies by an activity factor to cover the rest. The result is your total daily energy expenditure, often shortened to TDEE.

Take a 30-year-old man who is 5 ft 9 in (175 cm) and weighs 159 lb (72 kg). His resting burn works out to about 1,669 calories a day. What he needs in total depends on how active he is:

A woman of the same age, height and weight would have a resting burn of about 1,503 calories, because the formula subtracts 166 calories to reflect the average difference in body composition.

Calories for losing or gaining weight

Eat fewer calories than you burn and your body makes up the difference from its stores. A common rule of thumb is that a pound of body fat holds roughly 3,500 calories, so a 500-calorie daily shortfall adds up to about a pound a week. Treat that as a starting estimate: as you lose weight your body needs less energy, so the same intake produces slower loss over time.

• Health authorities such as the US CDC describe 1 to 2 pounds a week as a sustainable rate of loss.
• Very low intakes, commonly given as under 1,200 calories a day for women or 1,500 for men, are hard to keep nutritionally adequate and are best followed only with medical supervision.
• To gain weight, a surplus of 250 to 500 calories a day combined with strength training favors muscle over fat.

Calories are not all that matters

Two diets with the same calories can leave you feeling very different. Protein and fibre keep you full for longer, and protein helps preserve muscle while you lose weight. Each gram of protein or carbohydrate provides 4 calories, and each gram of fat provides 9, which is why small amounts of oils, nuts and dressings add up quickly.

How accurate is this?

Mifflin-St Jeor is considered the most reliable of the simple formulas, but it predicts an average. Real needs commonly differ by 10% or more depending on muscle mass, genetics, hormones and how much you move without noticing. Activity level is the biggest source of error, and most people rate themselves higher than they are.

The practical approach is to treat the result as a first guess. Eat at that level for two to three weeks, watch what your weight does, and adjust by 100 to 200 calories at a time.

Related tools

The BMR calculator shows your resting burn on its own. The BMI calculator and body fat calculator help you decide whether weight change is a sensible goal, and the steps to calories calculator estimates what walking adds.

This page gives general information, not medical advice. Speak to a doctor or registered dietitian before making significant changes to your diet, particularly if you are pregnant, under 18, managing a medical condition, or have a history of disordered eating.