Calorie calculator: how many calories do you need a day?

Fill in your sex, age, weight, height and how much you move, and the calculator below shows your resting energy use (BMR) and the calories that keep your weight stable (TDEE).

How to use the calorie calculator

You need five pieces of information, and it takes about a minute. Use a recent weight from your own scales; a number from last year can shift the result by a few hundred calories.

The tool accepts weights up to 400 kg and heights between 100 and 250 cm. If a value falls outside that range, you see a message asking you to check your entries.

Choosing your activity level honestly

This is the step where most estimates go wrong. Pick the description that matches an ordinary week, not your best week, and not the week you are planning to have.

The calculator starts on light activity because many readers do some walking. If you mostly sit and have joint pain that limits walking, the first option is probably closer to the truth.

When you are between two levels, choose the lower one. Equations and self-reported activity both tend to lean on the generous side, and it is easier to add food later than to wonder why the scales are creeping up.

Reading your result

After you press Calculate, three lines appear. Each is rounded to the nearest 10 so the number does not look more exact than it really is.

• Calories to keep your weight: your estimated TDEE. This is the headline number.
• Calories at rest (BMR): what your body would burn if you stayed in bed all day, awake but completely still.
• In kilojoules: the same TDEE expressed in kJ (1 kcal = 4.184 kJ), useful if food labels in your country show kilojoules first.

Think of your TDEE as the middle of a band rather than a line. A day 150 kcal above or below it makes no meaningful difference; what counts is the average across weeks.

Two worked examples

Seeing the sums with real numbers makes the result easier to trust, and easier to question.

Example 1. A woman aged 52, 165 cm tall, weighing 110 kg, who walks to the shops a few times a week. Her BMR is 10 × 110 + 6.25 × 165 − 5 × 52 − 161, which comes to about 1,710 kcal. With light activity (× 1.375) her maintenance level is roughly 2,350 kcal, or about 9,840 kJ.

Example 2. A man aged 45, 180 cm tall, weighing 130 kg, with an office job and no regular exercise. His BMR is 10 × 130 + 6.25 × 180 − 5 × 45 + 5, which the calculator shows as about 2,210 kcal. Mostly sitting (× 1.2) gives a TDEE of around 2,650 kcal.

Both numbers surprise many people because they are higher than the often-quoted “2,000 calories a day”. That figure is a labelling convention, not a personal target. Larger bodies genuinely need more fuel.

How are your daily calorie needs calculated?

The calculator uses the Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition. It is the standard choice in many clinics and dietetic practices for adults.

Where the equation comes from

Mark Mifflin, Sachiko St Jeor and colleagues measured the resting energy use of 498 healthy adults aged 19 to 78 with indirect calorimetry, a method that calculates energy burned from the oxygen you breathe in and the carbon dioxide you breathe out. Almost half of the group, 234 people, were living with obesity.

That detail matters for our readers. Many older formulas were built mainly on slimmer people. The team also found that the 1919 Harris-Benedict equations, still common online, overestimated measured resting energy use by about 5% in their sample.

A systematic review by Frankenfield and colleagues compared the main prediction equations in adults with and without obesity. Mifflin-St Jeor came out as the most reliable: it predicted resting metabolic rate within 10% of the measured value in more people than any other equation. It was still wrong by more than 10% for some, which is why we call the result an estimate.

Where the activity multipliers fit in

The five multipliers (1.2, 1.375, 1.55, 1.725 and 1.9) are a long-standing convention in nutrition practice. They describe how much energy daily life adds on top of your resting needs.

Scientists express the same idea as the physical activity level, or PAL: total daily energy use divided by basal energy use. An international FAO/WHO/UNU expert group grouped lifestyles into bands that you can compare with the calculator’s options.

The expert group noted that a PAL of 2.40 or more is hard to keep up for long. You may notice that the calculator’s lowest options sit below the FAO “sedentary” band. That is a deliberate, cautious choice for people who move very little, for example because of pain or a health condition.

Where your daily energy goes

Your body spends energy in three main ways. For most people, the basal metabolism is the largest share: keeping organs working, cells repaired and body temperature steady.

The second part is digesting and storing food, sometimes called the thermic effect of food. The third, and the one that varies most between people and between days, is movement: everything from standing and fidgeting to walking and planned exercise.

That third part is also the one you can change most easily. Even a daily 20-minute walk shifts your TDEE upward a little, and it brings benefits for mood, blood sugar and joints that have nothing to do with calories.

How do body size and age change your energy needs?

A heavier body burns more energy at rest and during movement than a lighter one of the same height. Part of the extra weight is fat-free mass, such as muscle, organs and bone, which is metabolically active.

This is why people living with obesity rarely have a “slow metabolism” in absolute terms. The difficulty usually lies elsewhere: appetite signals, the food environment, stress, sleep, medicines and genetics and biology.

Age has a smaller effect than many people think. A large study in Science, pooling energy measurements from people aged 8 days to 95 years, found that energy use adjusted for body size stays fairly stable from about 20 to 60 years and declines after that.

The formula simply takes off a modest 5 kcal for each year of age, a rough stand-in for that pattern.

What happens to your number after weight loss

As you lose weight, your maintenance level comes down, because there is less body to maintain and to carry around. Research also shows that the body tends to adapt: energy use falls somewhat further than the weight loss alone would predict, and appetite often increases.

A review by Kevin Hall and Scott Kahan describes how this combination makes keeping weight off harder than losing it. It is biology, not a lack of willpower. In practice it means you should recalculate after every 5 kg or so, and it explains why our page on weight regain focuses on long-term habits.

How can you check your estimate in real life?

A formula averages over hundreds of people. Your own body is the best laboratory, and a simple two- to four-week check turns the estimate into something personal.

1. Eat close to your calculated TDEE for two to four weeks. Use your normal foods; there is no need for perfection.
2. Weigh yourself at the same time a few mornings a week, after the toilet and before breakfast.
3. Look at the trend, not single days. Water, salt and hormones can move the scales by a kilo or more overnight.
4. Adjust in small steps. If your weight is steadily rising, your real maintenance is probably lower; if it is steadily falling, it is higher. Change your intake by 100 to 200 kcal and watch again.

If weighing yourself makes you anxious or triggers unhelpful thoughts, skip this method. You can use how your clothes fit, your energy levels or a waist measurement instead, or simply focus on food quality and movement without tracking numbers.

Limits: when the calculator is less useful

Every prediction equation has blind spots. The result is less reliable, or not appropriate at all, in these situations.

• Under 18. Children and teenagers are still growing, and their needs are calculated differently. The tool only accepts ages from 18. Our page on obesity in children explains why dieting is not the approach for young people.
• Pregnancy and breastfeeding. Your energy needs change from trimester to trimester and while breastfeeding. Follow your midwife or doctor, and do not use this result to cut calories.
• Very high body weight. The original study included people with obesity, but fewer people at the very highest weights. At those weights, prediction errors can be larger, so the real-life check above matters even more.
• Unusual body composition. Very muscular people, people with an amputation and people with conditions that change muscle mass may get a less accurate estimate.
• Illness and some medicines. Thyroid disorders, recent surgery, serious illness and certain medicines can raise or lower energy use.
• Hormone therapy. If your body composition has changed because of hormone treatment, ask your doctor which setting is closest to your situation.

Talk to your doctor or a dietitian before changing what you eat if you take medicines that can cause low blood sugar (such as insulin or sulfonylureas), have kidney or heart disease, or have ever lived with an eating disorder. Counting calories is not helpful for everyone; for some people it does more harm than good.

What to do with your number

A calorie figure is only useful if it helps you make everyday choices. Here is how to turn it into small, steady steps.

If you want to keep your weight stable

Use your TDEE as a rough daily budget and spread it over regular meals. Many people find that three meals and a planned snack keep hunger calmer than grazing or skipping breakfast.

Fill most of the plate with vegetables, fruit, whole grains, pulses and a portion of protein. Our free 7-day eating plan shows what this can look like across a week, without weighing every gram.

If you want to lose weight

You do not need to cut hard. A moderate daily reduction below your TDEE is usually enough. The calorie deficit calculator uses the same formula, adds the pace you choose and never suggests less than a safe minimum.

Once you have a daily target, the macro calculator turns it into grams of carbohydrate, fat, protein and fibre, so you know what to put on your plate.

Move a little more, at your level

Walking is the simplest way to nudge your activity level up a notch. Start with a few minutes after a meal and add time week by week; our walking guide explains how to build up without sore knees.

For strength and fitness, the free Start workouts are designed for people living with obesity, joint pain or no exercise history. Many sessions can be done partly seated.

After a month of regular walking or workouts, it may be time to choose the next activity level in the calculator and see how your maintenance number changes.

Get free support

Numbers are easier to use with someone to talk them through. You can book a free video meeting (in English) with Obesity Foundation to discuss food, movement and realistic goals.

A free Obesity Foundation Club account keeps the eating plans, workouts and calculators in one place, at no cost and without a subscription.

Related calculators

• Calorie deficit calculator: a daily target for gentle weight loss, with safe minimums built in.
• Macro calculator: split your calories into carbohydrate, fat, protein and fibre.
• Calories burned calculator: estimate what a walk or workout adds to your day.