Health & Fitness Calculators
Thirteen calculators for body composition, energy and training — built on the standard clinical and sports-science equations, with their limits stated.
Two clusters: what you are, and what you burn
Body composition tools describe your current state — the BMI Calculator, the Body Fat Calculator and the Ideal Weight. Energy tools describe your requirements — the BMR Calculator, the TDEE Calculator and everything downstream of them. Most people want both: composition tells you where you are, energy tells you what to do about it.
The order that makes the numbers make sense
Work out your basal metabolic rate first, then multiply by activity to get TDEE, then set a target above or below it. The Calorie Calculator turns that target into a daily figure, the Macro Calculator splits it into protein, carbohydrate and fat, and the Protein Calculator sets the floor that protects muscle while you are in a deficit. Skipping to the calorie number without knowing your TDEE is why so many targets feel arbitrary.
Training intensity and recovery
The Heart Rate Zones converts your maximum heart rate into five training zones, which is the difference between "run hard" and a specific, repeatable effort. The Pace Calculator works the same job from the other end, turning a goal finish time into the pace per kilometre you need to hold. The Sleep Calculator covers the part that actually produces the adaptation, timing bedtimes so you wake between 90-minute cycles.
Every one of these is an estimate
BMI cannot distinguish muscle from fat. Predictive BMR equations carry roughly a 10% error band. Maximum heart rate formulas are population averages with wide individual variation — a genuinely normal person can be 15 beats either side of the predicted figure. Body-fat estimates from tape measurements are less accurate than a DEXA scan by a wide margin. Use these numbers as starting points and adjust from your own results over two to three weeks.
When to stop calculating and ask someone
These tools are for general information and are not medical advice. If you are pregnant, managing a chronic condition, taking medication that affects weight or appetite, recovering from an eating disorder, or under 18, talk to a clinician before acting on any target here. The Due Date Calculator in particular gives an estimate based on a standard 280-day gestation — your midwife's dating scan is the authority.