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BMI Calculator

Compute your Body Mass Index and healthy weight range, entirely in your browser.

How BMI Calculator works

The BMI Calculator computes your Body Mass Index using the standard WHO formula. Enter your weight and height in metric (kg/cm) or imperial (lb/in) units and get your BMI value, your WHO category, and the healthy weight range for your height in under a second. All arithmetic runs locally in your browser so your measurements stay on your device.

BMI is a population-level screening tool, not a clinical diagnosis. It does not account for muscle mass, bone density, age or sex distribution. A highly muscular athlete and a sedentary person of identical height and weight receive the same BMI score. Treat the output as a reference starting point, not a substitute for a consultation with a qualified healthcare professional.

Written by Bastien Sulyan

How to use BMI Calculator, step by step

  1. Select your unit system: Metric (kg and cm) or Imperial (lb and in).
  2. Enter your body weight.
  3. Enter your height.
  4. Read your BMI value and WHO category from the result panel.
  5. Check the healthy weight range displayed for your height.

Common use cases

  • Tracking your weight trend over several months to see whether you are moving toward or away from a normal BMI range.
  • Comparing your BMI against WHO reference categories before an annual health check-up.
  • Helping a family member understand what a healthy weight range looks like for their height.
  • Screening whether a change in diet or exercise over the past quarter has shifted your BMI category.

Frequently asked questions

Does the BMI calculator send my measurements to any server?

No. Every calculation runs entirely inside your browser tab using plain JavaScript arithmetic. Your weight and height are typed locally, computed locally, and never transmitted anywhere. You can disconnect from the internet after the page loads and the calculator keeps working.

What is the BMI formula?

In metric units: BMI = weight (kg) divided by height (m) squared. For example, a person who weighs 70 kg and stands 1.75 m tall has a BMI of 70 divided by (1.75 x 1.75) = 22.9. In imperial units the NIH formula is: BMI = 703 x weight (lb) divided by height (in) squared.

What do the WHO BMI categories mean?

The World Health Organization defines four main categories: Underweight is a BMI below 18.5, Normal weight runs from 18.5 to 24.9, Overweight covers 25 to 29.9, and Obese is 30 and above. These are population reference ranges used for public health research, not individual clinical assessments.

Can BMI be wrong for muscular or athletic people?

Yes, commonly. BMI uses total body weight, not fat mass. A 90 kg powerlifter at 1.80 m gets a BMI of 27.8, which sits in the overweight range, even if their body fat percentage is 12 percent. For a more complete picture, use the body fat calculator (US Navy circumference method) as a second data point.

Are there separate BMI references for children or seniors?

The adult WHO thresholds (18.5, 25, 30) apply from age 18 upward. For children and adolescents, BMI is interpreted against age- and sex-specific growth charts with different cutoffs. This calculator uses the adult thresholds only.

Is a BMI result medical advice?

No. The result is for general information only. BMI does not diagnose any condition. Always consult a qualified healthcare professional before making decisions about your diet, exercise or medical care.

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