Nutrition Calculators
Six calculators, all free, no sign-up, and no results withheld until you hand over an email address. The formula behind each one is listed below, so you can check the maths yourself.
Calorie Calculator
Your daily calorie target from height, weight, age and activity level.
Mifflin-St Jeor BMR × activity multiplier
Macro Calculator
Splits your calorie target into daily protein, carb and fat grams.
Mifflin-St Jeor, then goal-based protein per kg
Protein Calculator
How much protein you need per day for your bodyweight and goal.
1.6 g/kg maintenance · 2.0 fat loss · 2.2 muscle gain
Water Intake Calculator
A daily water target based on bodyweight and how much you train.
35–45 ml per kg bodyweight, by activity level
BMI Calculator
Your BMI and what the range actually means — including its limits.
weight (kg) ÷ height (m)²
Body Fat Calculator
Estimates body-fat percentage from tape measurements.
U.S. Navy circumference method
These are estimates, not medical advice. Formulas are population averages — your own numbers will vary. Every formula, its source paper and the point at which it stops being reliable are set out in the methodology. Talk to a healthcare provider or registered dietitian before making significant dietary changes.