The Body calculators answer one practical question: where does your body stand today? They turn a few simple measurements — height, weight and a couple of tape measurements — into numbers you can act on: your Body Mass Index (BMI), an estimate of your body fat percentage, a sensible target weight range and the calories your body burns at complete rest (BMR).

They also check where fat sits on your body. The waist-to-hip and waist-to-height ratios use tape measurements to flag abdominal fat — the pattern most strongly linked to cardiometabolic risk — using the WHO 2008 cut-offs and the UK NICE NG246 guidance respectively.

None of these tools is a lab test. They are estimates built on published, widely referenced methods — WHO BMI categories, the U.S. Navy circumference formula, the Devine, Robinson, Miller and Hamwi ideal weight equations, and the Mifflin-St Jeor equation — and every page shows the formula and a worked example so you can check the maths yourself.

Who they are for

These calculators suit anyone who tracks their weight, lifts weights or is starting a nutrition plan. A couple of honest caveats: BMI cannot tell fat from muscle, so very muscular people, older adults and athletes should treat it as a starting point rather than a verdict. The body fat and ideal weight tools add useful context to BMI, and the BMR calculator gives you the resting energy you build a meal plan around.

How to use the results

Measure consistently — the same time of day, the same method and the same clothing. For body fat, measure first thing in the morning with the tape snug against bare skin. For everything else, watch the trend over weeks rather than a single numerical result: weight moves up and down with hydration, meals and sleep.

If your goal is to change your weight or body composition, pair these numbers with the Nutrition calculators (calories, macros and hydration), and take a result to a healthcare provider before making significant changes.