Calorie Calculator

About this Calorie Calculator

The Calorie Calculator estimates how many calories your body uses in a day. It first finds your basal metabolic rate, or BMR, which is the energy needed at complete rest, using the Mifflin-St Jeor equation. It then multiplies that number by an activity factor to estimate your total daily energy expenditure, called TDEE, and shows calorie targets for steady weight loss or gain. The results are estimates for adults, not medical advice.

Many people hear that they should eat a certain number of calories without knowing where the number comes from. This calculator makes the logic visible. Your body spends energy even when you are lying still, and much more when you move, so a fair estimate depends on your size, age, sex and activity. By seeing your maintenance level first, you can choose a gentle surplus or deficit rather than guessing or following a generic 2,000 calorie figure.

For related tasks, try BMI Calculator, Age Calculator or Weight Converter.

How the calculation works

BMR for men equals 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age in years plus 5. For women the last number is minus 161 instead of plus 5. TDEE equals BMR multiplied by an activity factor: 1.2 for sedentary, 1.375 for light, 1.55 for moderate, 1.725 for very active and 1.9 for extra active. Roughly 500 calories a day below or above TDEE changes weight by about half a kilogram, or one pound, a week.

How to use it

1. Choose metric or imperial units and enter your sex, age, weight and height.
2. Select the activity level that best matches a typical week.
3. Press Calculate calories to see your BMR, maintenance calories and targets for losing or gaining weight.

Practical example

A 30-year-old man who weighs 80 kg, is 180 cm tall and exercises three to five days a week has a BMR of 10 times 80 plus 6.25 times 180 minus 5 times 30 plus 5, which is 1,780 calories. Multiplied by 1.55 for moderate activity, his maintenance level is about 2,759 calories a day.

A 28-year-old woman who weighs 65 kg, is 165 cm tall and has a light activity level has a BMR of 10 times 65 plus 6.25 times 165 minus 5 times 28 minus 161, which is about 1,380 calories. Her maintenance level is about 1,898 calories a day, and a target 500 calories lower would be about 1,398, which is still above the commonly cited 1,200 calorie minimum.

Things to double-check

The activity factor is the part people get wrong most often. Choose the level that matches your normal week, not your best week. An office job with three gym sessions is usually moderate or light, not very active. The tool is designed for adults, and it is not suitable for pregnancy, breastfeeding, children, athletes in heavy training or people with medical conditions that change energy use. Ask a doctor or dietitian in those cases.

What a calorie is

A calorie in nutrition is a kilocalorie, the amount of energy needed to warm one kilogram of water by one degree Celsius, and it equals 4.184 kilojoules. Food labels use the word Calorie with a capital C or the abbreviation kcal for the same unit. Your body gets calories from carbohydrate, protein, fat and alcohol, and uses them to power the heart, brain, muscles and everything else. If you take in more energy than you use, the surplus is stored, mostly as fat. If you take in less, the body draws on its stores. This balance is the basis of any calorie target.

BMR: the energy of simply being alive

The basal metabolic rate is the energy your body needs at rest in a comfortable temperature, without moving or digesting food. It powers breathing, circulation, temperature control and the repair of cells. For most people it makes up about 60 to 70 percent of the calories they burn in a day. BMR is higher in people who are larger, younger, male and carry more muscle, because muscle uses more energy than fat. It tends to fall with age and with very low calorie diets. The calculator estimates your BMR from your sex, age, weight and height.

The Mifflin-St Jeor equation

In 1990 Mifflin and St Jeor published a formula based on measurements of several hundred adults. It estimates the resting energy in calories as ten times weight in kilograms, plus 6.25 times height in centimetres, minus five times age in years, then plus 5 for men or minus 161 for women. Later reviews found it one of the more reliable equations for healthy adults, which is why many dietitians use it. It is still an average. Two people with the same numbers can differ by a few hundred calories because of muscle mass and genetics.

Activity factors and TDEE

Your total daily energy expenditure includes the energy of movement, exercise and digesting food on top of BMR. The usual way to estimate it is to multiply BMR by an activity factor: 1.2 for little or no exercise, 1.375 for light exercise one to three days a week, 1.55 for moderate exercise three to five days, 1.725 for hard exercise six or seven days and 1.9 for very hard training or a physical job. These factors are rough. If you are unsure between two levels, pick the lower one, because people tend to overestimate how active they are.

Losing weight safely

To lose weight you need to eat less than you spend. A deficit of about 500 calories a day is often suggested as a steady pace of roughly half a kilogram, or one pound, a week, because about 3,500 calories correspond to a pound of body fat in the usual rule of thumb. Real weight loss is not perfectly linear, since water and the body's adaptation change the numbers. Aim for gradual change, keep protein adequate, and avoid dropping below the minimum levels of about 1,200 calories for women and 1,500 for men unless a doctor supervises.

Gaining weight and building muscle

To gain weight you need a surplus. A modest surplus of 250 to 500 calories a day is common advice for adding weight gradually, which is roughly a quarter to a half kilogram a week. A bigger surplus mostly adds fat. If your goal is muscle, combine the surplus with resistance training and enough protein, and track your progress in the mirror and on a tape measure, not only on the scale. People who are underweight for medical reasons should consult a doctor before changing their diet, because the cause matters.

Why the numbers are only estimates

Population formulas cannot know your body composition, hormones, sleep, stress, medications, climate or the exact way you move during the day. Studies comparing predicted and measured resting energy find that most healthy adults fall within about 10 percent of the estimate, but some individuals are further off. Food labels are also approximate, and a portion that you estimate by eye can be wrong by a lot. For these reasons, treat the calculator as a starting point. Follow your weight and energy for two to four weeks and adjust the intake by 100 to 200 calories if the trend is not what you intended.

Using the results with food tracking

Once you know your target, compare it with what you eat. Food labels list calories per serving, and nutrition databases cover unlabelled foods. Weigh food on a kitchen scale for the best accuracy, because eyeballed portions of foods like rice, oil, nuts and peanut butter are often underestimated. Many people find it enough to track for a week to learn typical portions, then eat by habit. Do not let the numbers become stressful. If counting calories affects your mood or leads to restrictive eating, step back and talk to a professional.

Who should be careful

Calorie formulas are meant for healthy adults. Children and teenagers are still growing and need guidance from a paediatrician or dietitian. Pregnant and breastfeeding women have higher needs. People with diabetes, thyroid conditions, eating disorders, kidney or heart disease should follow the advice of their medical team instead of an online estimate. Very low targets can cause fatigue, nutrient deficiencies and loss of muscle. The calculator shows a warning when a target falls below commonly cited minimums, and that warning should be taken seriously.

Common mistakes

People often overestimate their activity level, forget that the BMR changes as weight changes, or choose a deficit that is too large. Others compare their number with a friend's, even though age, height and muscle differ. Mixing units is another trap, such as entering pounds in a kilogram field, which is why the tool lets you switch units. Some people count exercise calories twice, by choosing a high activity level and then eating back what a watch says they burned. Use one method consistently and check the trend over several weeks.

Tips, privacy and limits

Recalculate every few months or after your weight changes by about 5 kilograms, because your needs change with it. Remember that sleep, protein, fibre, walking and strength training matter for health beyond the calories. The values that you type are processed in your browser and are not sent to Dekuz or stored. This tool is for general information and is not medical advice. If you have health conditions, take medication or are planning a large change in your diet, please speak to a doctor or registered dietitian.

Frequently asked questions