Fitness guides and calculators. Free calculators and clear guides to understand your body: body fat, BMI and how to improve your physique.

Calculators

A tape measure and two minutes: your estimated body fat percentage using the formula the United States Navy uses.

Your body mass index in seconds, what it means according to the WHO and, above all, what BMI can't tell you.

What body fat percentage is healthy, what counts as athletic and why your ideal number depends on your sex and your goals.

From hospital scanners to a tape measure: how far off each method is, what it costs and which one to use to track your progress.

Yes, you can lose fat and build muscle at the same time. Here's who manages it most easily and how to set up your diet and training.