Calorie Calculator – Daily Calories You Need

Calorie Calculator — How Many Calories Do I Need a Day?

Your daily calorie needs depend on your age, size, sex and how active you are. Use this calculator for a sensible estimate.

Last updated 10 October 2026 · Written for patients in Ireland

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How it works

The calculator estimates the energy your body uses at rest (using the Mifflin-St Jeor equation) and multiplies it by your activity level. To lose about half a kilo a week, most people need around 500 fewer calories a day.

Healthy weight loss

Aim for slow, steady change rather than crash diets
Focus on vegetables, fruit, wholegrains, lean protein and water
Build activity into your day
Get advice first if you have a medical condition, are pregnant or breastfeeding

Frequently asked questions

How many calories should I eat to lose weight?

For most people, about 500 calories a day fewer than they need to maintain their weight — but not too few. The calculator gives you both figures.

Are calorie calculators accurate?

They give a reasonable estimate. Your actual needs can vary by a few hundred calories.

Official sources and further reading

HSE: healthy eating

This page is general information for patients in Ireland, not a diagnosis or personal medical advice. If you are worried about your health, speak to a doctor. In an emergency call 112 or 999.

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