UK fitness, body and diet calculators

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.

BMIMacrosProteinRunning paceHeart-rate zones
Calorie and TDEE calculator

How many calories do you burn?

Your details
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

Pick one, start instantly
Diet

Calorie and TDEE

Daily energy burn to maintain, lose or gain.

Mifflin-St Jeor Body

BMI and waist-to-height

Two reads on body shape, with the NHS bands.

NHS bands Diet

Macro calculator

Protein, carbs and fat for your calorie target.

Percent of intake Body

Protein calculator

Daily grams by bodyweight, activity and goal.

g per kg Running

Running pace

Pace, time and distance, converted three ways.

min per km Running

Age-grade

How your time rates for your age and sex.

WMA tables Body

Heart-rate zones

Five training zones from resting and max HR.

Karvonen Running

VO2 max estimate

Aerobic fitness from a recent race result.

Daniels Data

Where you stand

How your numbers compare to the UK average.

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.

Every result shows its equation. Mifflin-St Jeor, Karvonen, Riegel and the NHS bands, named on each tool so you can check the maths. Benchmarked to official UK data. NHS Health Survey for England, Sport England Active Lives and the NDNS. Informational, not medical advice. Estimates to guide you, not a diagnosis.
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FitCalcs Editorial

Calculators and Data Desk, FitCalcs

FitCalcs' editorial desk builds and documents the calculators, citing the underlying equation and the UK dataset behind every number. Health-related tools are editorially reviewed, with figures cited to named UK sources.

Last reviewed: 12 June 2026