Calorie Calculator
Estimate how many calories you burn each day, and how many to eat to lose or gain weight.
About this tool
Uses the Mifflin-St Jeor equation for resting energy (BMR) and standard activity multipliers to estimate the calories you burn in a day. It is an estimate for healthy adults, not medical advice.
Find out roughly how many calories your body uses in a day, so you can plan meals to keep your weight steady, lose weight slowly or build up. Enter your sex, age, weight, height and how active you are to get your resting calorie burn (BMR), your daily maintenance calories and simple targets for losing or gaining about half a kilogram a week. It runs in your browser and nothing is saved.
How to use the Calorie Calculator
- Choose your sex and enter your age.
- Enter your weight in kilograms and your height in centimetres.
- Pick the activity level that best matches a normal week.
- Read your maintenance calories and the targets to lose or gain weight.
A 30-year-old man, 70 kg and 175 cm
His BMR is 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,648.75, about 1,649 kcal a day at complete rest. With moderate exercise the multiplier is 1.55, so he burns about 1,649 × 1.55 = 2,556 kcal a day. Eating about 500 kcal less, 2,056 kcal, would lose roughly 0.5 kg a week; eating 3,056 kcal would gain about the same.
How the estimate works
Your basal metabolic rate (BMR) is the energy your body uses at rest for breathing, circulation and keeping warm. This calculator uses the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for men or minus 161 for women. That is multiplied by an activity factor from 1.2 (little exercise) to 1.9 (very hard exercise) to estimate total daily energy expenditure. A deficit of about 500 kcal a day adds up to roughly 3,500 kcal a week, a common rule of thumb for half a kilogram of body fat, although real weight loss slows as you get lighter. Most people should not go below about 1,200 kcal (women) or 1,500 kcal (men) a day without medical supervision. Equations can be 10% out either way for any one person, so watch how your weight actually changes over a few weeks and adjust.
Frequently asked questions
How many calories should I eat a day?
It depends on your size, age, sex and activity. Many adults need about 1,800 to 2,400 kcal (women) or 2,200 to 3,000 kcal (men). Use the calculator for a personal estimate.
What is the difference between BMR and maintenance calories?
BMR is what you burn at complete rest. Maintenance calories add the energy you use moving, working and exercising, so they are always higher.
How do I convert calories to kilojoules?
Multiply kcal by 4.184. 2,000 kcal is about 8,368 kJ. South African and Australian food labels often show kJ.
Is this accurate for athletes or during pregnancy?
Not very. Very muscular people burn more than the equation predicts, and pregnancy and breastfeeding change energy needs. Ask a dietitian or doctor.