Calorie Calculator
Free to use. Runs in your browser: your files and text are not uploaded.
This tool gives general information only. It is not medical advice.
Enter a few details to estimate the calories you use in a day, and the daily amounts linked with slow weight loss or gain.
How to use it
- Choose your sex and type your age.
- Choose units, then type your height and weight.
- Choose the activity level that best matches a normal week.
How it works
Step 1: resting energy. The tool estimates your basal metabolic rate (BMR), the calories your body uses at complete rest, with the Mifflin-St Jeor equation:
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Step 2: activity. BMR is multiplied by an activity factor:
| Activity level | Factor |
|---|---|
| Little or no exercise | 1.2 |
| Light exercise, 1 to 3 days a week | 1.375 |
| Moderate exercise, 3 to 5 days a week | 1.55 |
| Hard exercise, 6 to 7 days a week | 1.725 |
| Very hard exercise or a physical job | 1.9 |
Example: a 30-year-old man, 175 cm and 70 kg, with light exercise. BMR = 700 + 1,093.75 − 150 + 5 = 1,648.75. Daily need = 1,648.75 × 1.375 = about 2,267 calories.
Step 3: weight change. The other lines add or subtract 250 or 500 calories a day.
About the 500-calorie rule
The rule comes from the old estimate that 1 pound of body fat holds about 3,500 calories. Researchers have since shown that it overstates long-term weight loss, because the body uses less energy as weight falls. Treat the figures as a rough guide for the first weeks, not a prediction.
Limits
- The equation was developed on adults. It is not for children, or for pregnancy and breastfeeding, when needs are higher.
- People with a lot of muscle use more energy than the estimate, and people with little muscle use less.
- Harvard Health Publishing advises that intake should not fall below 1,200 calories a day for women or 1,500 a day for men, except under the supervision of a health professional. If a line shows less than that, do not follow it.
- Speak to a doctor or dietitian before a large change in diet, especially if you have a health condition.
Frequently asked questions
How many calories should I eat a day?
It depends on your age, sex, size and activity. This tool estimates the calories that keep your weight steady, then shows figures for losing or gaining weight.
How many calories do I cut to lose 0.5 kg a week?
The tool uses the common rule of about 500 calories a day below your maintenance level. Real weight loss varies between people and slows over time.
How accurate is the estimate?
It is a starting point. The equation behind it predicts resting energy use to within about 10% for most adults, and the activity level is a broad estimate on top of that.