How many calories should I eat a day?

The short answer

A commonly used reference is around 2,000 calories a day for women and 2,500 for men, which is the guidance the NHS uses for adults. The US Dietary Guidelines give broader ranges, roughly 1,600 to 2,400 calories a day for adult women and 2,000 to 3,000 for adult men, depending on age and activity. These are averages, not personal targets. Your own needs depend on your size, age, sex, body composition and how active you are.

The most practical approach is to start with an estimate, then adjust it based on what actually happens to your weight and energy over a few weeks.

What decides how much energy you use

Your daily energy use, often called maintenance calories or total daily energy expenditure, is made up of three main parts:

• Resting energy. The energy your body uses just to keep running: breathing, circulation, temperature and organ function. This is usually the largest part and is higher in larger and more muscular bodies.
• Movement. Exercise, plus all the everyday activity of walking, standing, housework and fidgeting. This is the part that varies most between people and between days.
• Digestion. A smaller amount of energy is used to digest and process food.

Age also plays a part. Energy needs tend to fall gradually through adulthood, partly because of changes in muscle mass and activity.

How calculators estimate your needs

Most apps and online calculators use a formula to estimate resting energy, then multiply it by an activity factor. One widely used formula is the Mifflin-St Jeor equation, which uses your weight, height, age and sex. The result is then multiplied by a number that reflects your typical activity.

For example, if a formula estimates someone's resting energy at 1,450 calories, and they are lightly active, their estimated maintenance would be about 1,450 × 1.375, or roughly 2,000 calories a day.

These formulas are useful starting points, but they are estimates. Two people with identical numbers can differ by a few hundred calories a day, and many people overestimate how active they are.

Turning an estimate into your number

The best way to find your real maintenance level is to test the estimate:

1. Eat around your estimated amount for two to four weeks, logging as consistently as you reasonably can.
2. Weigh yourself a few times a week at the same time of day and look at the weekly average rather than single readings.
3. If your average weight is stable, you are close to maintenance. If it is rising or falling, your real needs are a little lower or higher than the estimate.

Day-to-day weight moves with water, salt and digestion, so patience matters here. A trend over several weeks is much more reliable than any single morning.

If you want to lose or gain weight

To lose weight, you need to eat a little less than your maintenance level over time. A moderate gap is generally easier to sustain than an aggressive one. Our guide to the calorie deficit explains how to set one sensibly. To gain weight or build muscle, a modest surplus alongside strength training is the usual approach.

Very low-calorie diets should only be followed under medical supervision. If you are pregnant, breastfeeding, under 18, have a medical condition or a history of disordered eating, speak to a doctor or registered dietitian before setting a calorie target.

Calories are not the whole picture

Two days with the same calories can feel very different. Meals with enough protein, plenty of vegetables, fruit, whole grains and some healthy fats tend to keep people fuller and more energetic than the same calories from sugary snacks and drinks. Our guide to macros explains how protein, carbohydrate and fat fit into your total, and if counting every calorie does not suit you, see how to eat well without counting everything.