Calorie Calculator
This calculator estimates how many calories you need to maintain your weight, based on your BMR (basal metabolic rate) and how active you are.
To lose weight, eat below this number; to gain, eat above it. The NHS advises losing weight gradually — around 500 calories a day less.
How the calculation works
We believe numbers should be transparent. Here is the formula behind this calculator.
Worked example
Worked example: 80 kg, 180 cm, 30, moderately active male
Important assumptions
- Uses the Mifflin-St Jeor equation, one of the most accurate BMR formulas.
- Activity factors are estimates — a good tracker will be more precise.
- These are targets, not a diagnosis; consult a professional for medical advice.
Rates & official sources
Every calculation is based on the official rates and rules published by GOV.UK and HMRC.
Frequently asked questions
How many calories should I eat to lose weight?
The NHS suggests a 600 kcal daily deficit for steady weight loss, which typically means eating 300–500 kcal below your maintenance number. Avoid going below 1,200 (women) or 1,500 (men) a day.
What is BMR?
Your basal metabolic rate is the energy your body uses at complete rest — breathing, pumping blood and keeping you warm. It is the largest part of your daily calorie burn.
Is this calculator suitable for bodybuilding?
For gaining muscle, eat 300–500 kcal above maintenance with enough protein. The equation still applies, but athlete-level calorie needs can differ.
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View calculatorRelated guides
New to the topic? Read a plain-English guide on health & lifestyle, with worked examples and tips.
These calculations are estimates for guidance only and are not professional financial, tax or legal advice. UK rates and rules change, so always verify important figures with official GOV.UK / HMRC information or speak to a qualified professional. See our full disclaimer.