Calorie Calculator

This estimates how many calories your body uses in a day. It starts from your resting needs using the Mifflin-St Jeor equation, then scales that by how active you are. It also shows rough figures for losing or gaining weight gradually. It's a population estimate, so real needs can differ by a few hundred calories either way.

How to use it

1. Choose metric or imperial units.
2. Enter your sex, age, height and weight.
3. Pick the activity level that best matches a typical week.
4. Read your maintenance calories and your resting figure.

When it helps

• Getting a starting point for a nutrition plan.
• Understanding how much activity changes your needs.
• Sanity-checking a plan someone else gave you.
• Learning the difference between resting and total energy use.

Good to know

• Most people overestimate their activity level. If in doubt, pick the lower one.
• Change intake slowly and watch results over a few weeks rather than days.
• See a doctor or registered dietitian before making large changes, especially if you have a health condition.

The equation used

The Mifflin-St Jeor equation estimates resting energy: 10 times weight in kilograms, plus 6.25 times height in centimetres, minus 5 times age, then plus 5 for men or minus 161 for women. A 30-year-old woman at 70 kg and 170 cm comes out at about 1,451 calories. Multiplying by an activity factor from 1.2 to 1.9 gives total daily energy.

Studies have found this equation more accurate than older ones for most adults, though individual results vary.

Worked example: reading the result

With a light exercise factor of 1.375, that woman's maintenance is around 1,996 calories. Eating 250 below that is a gentle deficit, around 1,750. Over weeks, a 250 to 500 calorie difference is a common range for gradual change, but the best figure depends on you.

Track your weight and energy over three to four weeks to see whether the estimate fits, and adjust.

What calories don't tell you

Calories measure energy, not nutrition. A diet of 2,000 calories can be healthy or poor, depending on protein, fibre, vitamins and minerals. Sleep, stress, medication and hormones also affect weight and hunger.

If you have a medical condition, are pregnant, are under 18 or have a history of disordered eating, speak to a professional before using calorie targets.

Choosing an activity level

Sedentary means a desk job and little exercise. Light activity means exercise one to three times a week. Moderate means three to five sessions, and very active means daily hard training or a physical job. Being on your feet all day at work counts for more than a gym session.

If you're unsure, start with the lower option and adjust after a few weeks of real data.

Revisiting the estimate

Recalculate after any large change in weight or activity, since the estimate shifts with both. Recheck every couple of months.

Questions