How many calories should I eat a day? By age and sex

Most adult women need about 1,600 to 2,400 calories (kcal) a day and most adult men about 2,000 to 3,000 to keep their weight, depending on age and how active they are. The NHS rounds this to 2,000 kcal for an average woman and 2,500 for an average man. To lose weight, you take a moderate deficit off your own number; you don't jump to 1,200.

It was the first question I asked when I started counting, and the answers online ran from 1,200 to 3,000 kcal. Below is what I found in sources I trust.

How many calories a day by age and sex?

Adult women need about 1,600 to 2,400 kcal a day and adult men about 2,000 to 3,000, according to the table in the Dietary Guidelines for Americans 2020–2025, here in the short form the Merck Manual publishes. The numbers are kcal a day to keep your weight the same.

Who	Age	Sedentary	Active
Women	19–60	1,600–2,000	2,200–2,400
Women	61 and over	1,600	2,000
Men	19–60	2,200–2,600	2,600–3,000
Men	61 and over	2,000	2,400–2,600
Average woman	adult	2,000
Average man	adult	2,500

Source: Dietary Guidelines for Americans 2020–2025 (via the Merck Manual); the "average" rows are the NHS figures.

Younger, taller and heavier people sit near the top of a range, older and smaller people near the bottom. For me, "sedentary" means a desk job, driving to work and a bit of walking; "active" means walking at least an hour a day, physical work or training most days. If you're not sure, take the lower number.

The 2,000 on a US Nutrition Facts label is a reference, not a recommendation for you. The FDA says 2,000 calories a day is used as a general guide and your needs may be higher or lower. EU labels use the same 2,000 kcal as the reference intake of an average adult (Regulation 1169/2011).

How do I calculate my own number?

You can calculate your own calorie needs with the Mifflin–St Jeor equation, published in 1990 and still one of the most used. It estimates what your body burns at rest:

• Women: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161
• Men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5

Two examples. A woman of 35, 165 cm (5 ft 5 in) and 75 kg (165 lb): 750 + 1,031 − 175 − 161, about 1,445 kcal. A man of 40, 180 cm (5 ft 11 in) and 90 kg (198 lb): 900 + 1,125 − 200 + 5 = 1,830 kcal.

That is your basal metabolic rate, the energy your body uses lying still. You burn more because you walk, work and digest food, so the result is multiplied by an activity factor: 1.2 for mostly sitting, 1.375 for lightly active, up to 1.9 for a physical job. For the woman above, lightly active, that is about 1,985 kcal a day, inside the table's range. My calorie calculator does both steps. It's an estimate: let your weight over two or three weeks tell you if it fits.

How many calories should I eat to lose weight?

To lose weight, eat your maintenance number minus a moderate calorie deficit, usually about 275 to 550 kcal a day. My deficit calculator uses about 7,700 kcal per kilo of body fat, so 0.25 kg (about half a pound) a week is about 275 kcal a day less, and 0.5 kg (about a pound) about 550. The NHS suggests cutting around 600 calories a day. For the lightly active woman above, 550 less gives a target of about 1,435 kcal.

The CDC notes that people who lose weight at a gradual, steady pace are more likely to keep it off. I don't plan faster than 0.75 kg (about 1.7 lb) a week, and I'd rather sit at 0.25 to 0.5. When I overdid the deficit, I lasted two weeks and then ate back everything I had "saved".

Your number also moves as you lose weight, because a lighter body burns less. I recalculate every 4 to 5 kg (roughly 10 lb). The NIH's free Body Weight Planner builds this in: you enter your goal weight and when you want to reach it, and it plans both the loss and keeping the weight afterwards.

Is 1,200 calories a day enough?

For most adults, 1,200 kcal a day is a floor, not a goal: don't go below it without talking to your doctor. The same goes if you're pregnant or breastfeeding, have diabetes or another chronic condition, or have had problems with eating: then a professional should set the number, not a table online. Everything here is for adults (18 and over).

What does 1,800 calories look like?

An 1,800-calorie day fills up faster than you'd think: a piece of meat burek (250 g) alone is about 725 kcal, close to half of a 1,600-calorie day. Other examples from my calorie tables:

• Two hard-boiled eggs and a 40 g slice of whole-wheat bread: about 255 kcal, a breakfast that keeps me going until lunch.
• A plate of bean stew with smoked meat (350 g) and two slices of white bread: about 595 kcal.
• A medium banana: about 105 kcal.

The easiest savings are on the side: the third slice of bread, the oil, the drink.

Do I need to count calories every day?

You don't need to count calories every day forever. The first two or three weeks taught me the most: what 100 g of meat looks like and how much oil a "splash" really is. After that I count now and then, when my weight moves the wrong way.

Typing in every ingredient is the tedious part. That's why I'm building Calorko, an Android app where you photograph your plate and get a calorie estimate with a range, because a photo is never a kitchen scale.

In short

• Women: about 1,600–2,400 kcal a day to keep their weight; men: about 2,000–3,000.
• The 2,000 on food labels is a general guide, not your number.
• For your own number, use Mifflin–St Jeor or the NIH Body Weight Planner, and recalculate every 4–5 kg.
• To lose weight, take off about 275–550 kcal a day; don't go below 1,200 kcal a day without your doctor.