Is BMI accurate for everyone?

BMI is a rough screening tool, not a diagnosis. It overestimates body fat in muscular athletes and underestimates it in older adults with low muscle mass. Combine it with waist circumference, body fat % and clinical assessment.

Does BMI work for children?

Use BMI-for-age percentiles for anyone under 20, not the adult cut-offs. Our calculator flags this when you enter an age under 20.

Why are there different BMI cut-offs for Asian populations?

WHO recommends lower overweight (≥23) and obesity (≥27.5) thresholds for South and East Asian populations due to higher cardiometabolic risk at a lower BMI.

Is my health data stored?

No. Everything is calculated in your browser. No weight or height is sent to our servers.

BMI Calculator — Free Online Tool

What is the BMI Calculator?

The BMI Calculator is a free online calculator tools from Markvibe. Calculate Body Mass Index. It runs entirely in your browser — your data never gets uploaded — and works on desktop, tablet and mobile with no sign-up.

Reviewed by The Markvibe Team · Last updated 2026-06-28

Example

A worked example so you know exactly what to expect.

Input

(your input goes here)

Output

(the BMI Calculator runs in your browser and shows the result instantly)

How to use BMI Calculator

1Pick your unit system: metric (kg, cm) or imperial (lb, ft+in).
2Enter your weight and height — the BMI updates as you type.
3Read the category badge: underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), obese (≥30) per WHO classification.
4View where you sit on the BMI scale and how many kg/lb separate you from each adjacent category.
5Use the "healthy weight range" output to see the target weight range for your height.