Know your numbers, with the equation shown.
Free, built on official UK data, no sign-up. Start with the calorie calculator, then jump to any tool.
Calorie and TDEE calculator How many calories do you burn?
How this is worked out
Your basal metabolic rate (BMR) uses the Mifflin-St Jeor equation, the formula the British Dietetic Association and most clinicians use:
BMR = (10 x weight kg) + (6.25 x height cm) − (5 x age) + s
s = +5 for men, −161 for women
Your TDEE (total daily energy expenditure, the calories you burn in a day) is BMR multiplied by an activity factor of 1.2 to 1.9. Weight-change targets assume roughly 7,700 kcal per kg of body mass and cap the rate at a safe 0.5 to 1.0 kg per week.
Informational only, not medical or dietary advice. Editorially reviewed by FitCalcs, with each figure citing its source.
All calculators
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NHS and Sport England
FitCalcs is a set of free UK fitness, body and diet calculators. Every tool shows the exact equation it uses (Mifflin-St Jeor for calories, Karvonen for heart-rate zones, Riegel for race times) and the official UK data behind it, from the NHS Health Survey for England, Sport England Active Lives and the National Diet and Nutrition Survey. No sign-up, no email, just the maths. The figures are informational only and not medical advice.
Common questions
How do I work out how many calories I burn a day?
Estimate your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, then multiply it by an activity factor from 1.2 to 1.9. That gives your total daily energy expenditure (TDEE), the calories you burn in a day. The calculator above does both steps and shows the working. This is general information, not personalised dietary advice.
What are the TDEE activity multipliers?
Multiply your BMR by 1.2 for sedentary (little or no exercise), 1.375 for lightly active (1 to 3 days a week), 1.55 for moderately active (3 to 5 days), 1.725 for very active (6 to 7 days), and 1.9 for extremely active (a physical job or training twice a day). Pick the factor that best matches a normal week.
How accurate is a calculated calorie burn?
It is a good estimate, not a precise measurement. The Mifflin-St Jeor formula carries an average error of roughly 5 percent, and the activity factor is a rough guess on top, so use the result as a starting point. Watch your weight over a couple of weeks and adjust the target if it is not moving as expected.
Do the FitCalcs calculators need a sign-up or store my data?
No. Every tool is free and runs in your browser, with no account and no email required. We do not store the figures you enter, so your weight, height and other inputs stay on your device.
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Editor, FitCalcs
Oliver Mackman is the named editor of FitCalcs and a director of Best Business Loans Ltd (Companies House 16833937), the company that operates the site. He is accountable for its editorial standards, sourcing and corrections, and requires every result to cite the underlying equation and the named UK source behind it, with health tools carrying the appropriate not-medical-advice caveats.
Last reviewed: 12 June 2026