Body Composition Calculator

Complete body analysis: BMI, body fat percentage, ideal weight, daily calories (TDEE), and macro targets. Get all your fitness metrics in one comprehensive calculator.

Seven separate calculators share one input form here, and they draw on different subsets of it. Everything is converted to kilograms and centimetres first, then BMI, a healthy-weight window at BMI 18.5 to 24.9, body fat, lean and fat mass, four ideal-weight formulas, a Mifflin-St Jeor energy chain and a waist-to-hip ratio are each derived independently. Body fat has two routes. Enter a waist and neck measurement — plus a hip measurement if Female is selected — and the US Navy circumference formula runs; leave them blank and a BMI-based approximation runs instead, which is why the category row is tagged as an estimate and why age nudges the figure in that mode but not the other. The strongest single lever on Target Calories is the Activity Level dropdown, worth 1,216 calories across its five settings on the default profile, far more than any measurement you can adjust. Your Goal selection moves Target Calories by up to 800 and reshapes the macro split, but it never touches BMR or TDEE, which are computed before it applies. Two results behave in ways worth knowing. Ideal Weight is derived from height and gender alone — averaging the Robinson, Miller, Devine and Hamwi formulas — so it does not respond to your actual weight at all; the Weight Status line is what compares the two, and it only speaks up beyond a 5 lb or 2 kg tolerance. And Protein per kg falls as weight rises, because protein is a share of calories rather than a per-kilogram prescription. Circumference-based body fat carries roughly a three to four point error against DEXA, and the BMI route is looser still.