Calorie & macro calculator.

The simplified Mifflin-St Jeor equation estimates resting energy from weight, height, age and the selected reference equation. An activity factor gives estimated maintenance needs. The optional 10% reduction and 5% increase are planning assumptions, not guideline-prescribed targets. No rate or date of weight change is predicted. Resting energy is not your daily food allowance.

The sample macro split is 25% protein, 45% carbohydrate and 30% fat. It is an example, not the only suitable split. Rounded grams may differ slightly from the displayed energy total.

Before you use this calculator

These tools offer general information for adults. Results are estimates, not a diagnosis, treatment plan or prescription. Your clinician can help you decide what fits your health, medicines and goals.

General guidance for adults 18+ who are not pregnant or breastfeeding. Seek individual advice for eating disorders, significant illness, prescribed diets or medication-related appetite changes.

Your calculation happens in this browser. Do not enter your name or medical records. These tools do not assess medicine suitability or dosing.

Tests or treatment are recommended only when clinically appropriate. Laboratory charges are separate.

Sources and context

• EFSA: Dietary reference values for nutrient intakes

  Adult total water reference and carbohydrate/fat ranges. Total water includes food and drinks; published 2010.

• Mifflin et al. (1990): A new predictive equation for resting energy expenditure in healthy individuals

  Original resting-energy equation verified through indexed abstract; direct page retrieval was blocked by cookies. Activity multipliers and goal adjustment are separate assumptions.

• NICE NG246: Physical activity and diet

  Individualised nutrition, supported energy deficits and specialist supervision for low-energy diets; updated 8 January 2026.

• NIDDK: About the Body Weight Planner

  Useful comparator for adult-only scope and pregnancy/breastfeeding exclusions. Does not validate this site's simpler equation.

Sources checked in the supplied release pack on 18 October 2026. Clinical review by Dr Addinall and compliance review by Thomas are complete.