Calories & Nutrition tool
Calorie Calculator
Work out how many calories you need a day to keep, lose or gain weight, from your age, height, weight and activity. Mifflin-St Jeor formula. Free, nothing stored.
Nothing you enter leaves your device.
Inputs
Results
Enter values to see your results.
Simple steps
How it works
- 01
Enter your sex, age, height and weight, in metric or imperial units.
- 02
Choose how active you are on a typical week.
- 03
Select Calculate to see your maintenance calories and daily targets to lose or gain weight.
Good to know
Frequently asked questions
How is my daily calorie need worked out?
Your calories at rest (BMR) come from the Mifflin-St Jeor equation, then they are multiplied by an activity factor from 1.2 (little exercise) to 1.9 (very hard exercise or a physical job). The result is your maintenance calories, also called TDEE.
How are the weight-loss and weight-gain targets set?
A change of about 1 kg of body weight takes roughly 7,700 kcal, so losing 0.5 kg a week means eating about 550 kcal a day below maintenance, and 0.25 kg a week about 275 kcal below. Gaining works the same way above maintenance.
How accurate is the result?
It is an estimate. Real needs vary by about 10% between people with the same numbers. Track your weight for a few weeks and adjust by 100 to 200 kcal a day if it changes faster or slower than planned.
Why is there a warning about a minimum?
Targets below about 1,500 kcal a day for men or 1,200 kcal a day for women make it hard to get enough nutrients. Speak to a doctor or dietitian before eating that little.
Does it work for children, pregnancy or athletes?
No. The formula is for adults. Children, pregnant or breastfeeding women, and very muscular athletes have different needs; ask a professional.
Can I use pounds and inches?
Yes. Choose imperial units and the height and weight fields switch to inches and pounds; the values you typed are converted for you.
Is anything I enter stored or sent?
No. The calculation runs in your browser. Nothing you type is saved or sent to a server.
How it is calculated
Calories at rest (BMR) use the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. BMR is multiplied by an activity factor (1.2, 1.375, 1.55, 1.725 or 1.9) to give maintenance calories. Weekly targets add or subtract 7,700 kcal per kilogram, spread over seven days.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr 1990;51:241–7
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner
Last reviewed: October 14, 2026