BMI calculator

Updated 16 July 2026

Enter your height and weight and this calculator gives your body mass index (BMI) and where it lands in the World Health Organization adult categories: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is classed as obesity.

One honest caveat before you read your number: BMI cannot tell muscle from fat. Plenty of lifters sit in the overweight band with low body fat, so treat BMI as a population screening tool, not a verdict on your physique.

Units

Your BMI

…

Enter your height and weight to see your BMI.

WHO adult BMI categories
Category BMI range Worth knowing
Underweight Below 18.5 May indicate under fuelling for your training. Worth a conversation with a professional.
Healthy range 18.5 to 24.9 The range associated with the lowest health risk for most adults.
Overweight 25 to 29.9 Common for muscular lifters; pair with a body composition check before drawing conclusions.
Obesity 30 and above Associated with higher health risk. Training and consistency move this number reliably.

How to calculate your BMI

  1. 1 Choose your units Switch between kg and cm or lb and ft to match how you know your measurements.
  2. 2 Enter your height and weight Type in your height and weight; the calculator handles the metric or imperial formula for you.
  3. 3 Read your BMI and category See your BMI and WHO category, and remember it cannot tell muscle from fat, so lifters often read one band heavier.

How this is calculated

BMI is weight in kilograms divided by height in metres squared. In imperial units the same index is 703 × weight in pounds divided by height in inches squared. The category boundaries are the World Health Organization adult classification.

BMI was designed to screen populations, not to assess individuals. It cannot distinguish muscle from fat, says nothing about where fat sits, and the adult categories do not apply to children, pregnant women, or the very elderly. If your training goal is body composition, waist measurement and body fat estimates are the better numbers to watch.

Common questions

Is BMI accurate for people who lift weights?

It is systematically misleading for muscular people. BMI only knows your height and weight, so added muscle raises it exactly the way added fat does. If you train seriously, waist measurement, body fat estimates, and progress photos tell you far more than BMI.

What is a healthy BMI?

For most adults, 18.5 to 24.9. The ranges come from population studies of health risk, which is also their limit: they describe averages across millions of people, not any individual, and they apply to adults rather than children or pregnant women.

Should I try to change my BMI?

Chase the inputs, not the index. Consistent strength training, adequate protein, and a sensible calorie balance improve body composition; BMI follows on its own timetable. If your BMI sits far outside the healthy range in either direction, that is worth discussing with a healthcare professional.

BMI or body fat percentage, which should I track?

Body fat percentage is the better signal if you can measure it consistently, because it separates the tissue you want to keep from the tissue you may want to lose. BMI wins only on convenience: two numbers you already know, no equipment.

Choosing an app?

Honest comparisons of the AI workout apps, with verified prices and trials.