Body Mass Index (BMI) is a simple number calculated from your height and weight. It is used as a screening tool to identify whether a person is underweight, normal weight, overweight, or obese. BMI = weight (kg) ÷ height² (m).

What is a healthy BMI range?

According to the World Health Organization: below 18.5 is Underweight, 18.5–24.9 is Normal weight, 25–29.9 is Overweight, and 30 or above is Obese. These thresholds apply to most adults.

BMI is a useful population-level screening tool but has limitations for individuals. It does not account for muscle mass, bone density, age, sex, or body fat distribution. Athletes may have a high BMI despite low body fat. Always consult a healthcare professional for a full assessment.

How is BMI calculated in imperial units?

For pounds and inches: BMI = (weight in lbs × 703) ÷ height in inches². This calculator converts your feet and inches to centimetres and your pounds to kilograms before applying the standard formula.

What is my healthy weight range?

The healthy weight range shown below your result is the weight at which your BMI would be between 18.5 and 24.9 for your specific height. It gives you a practical target range rather than a single number.

Is this calculator private?

Yes. All calculations happen inside your browser using JavaScript. Your height and weight are never sent to any server, stored, or shared with anyone.

BMI Calculator — Calculate Your Body Mass Index Free

Height

Weight

— BMI

BMI scale (WHO)

Underweight < 18.5

Normal weight 18.5 – 24.9

Overweight 25 – 29.9

Obese ≥ 30

Enter your height and weight to calculate your Body Mass Index (BMI). Supports both metric (cm/kg) and imperial (ft/lbs) units. Results update instantly, and the calculator also shows your healthy weight range based on WHO guidelines. Everything runs in your browser — no data is ever sent to a server.

How it works

1
Choose your unit system Click Metric for centimetres and kilograms, or Imperial for feet, inches, and pounds. The inputs switch automatically.
2
Enter height and weight Type your height and weight into the input fields. Your BMI updates instantly as you type — no button required.
3
Read your result Your BMI value and weight category (Underweight, Normal, Overweight, or Obese) appear immediately. The healthy weight range for your height is shown below.

Your data stays private

All processing happens entirely in your browser. No files, text, or data are ever sent to our servers. You can disconnect from the internet and this tool will still work.

Frequently asked questions

What is BMI?: Body Mass Index (BMI) is a simple number calculated from your height and weight. It is used as a screening tool to identify whether a person is underweight, normal weight, overweight, or obese. BMI = weight (kg) ÷ height² (m).
What is a healthy BMI range?: According to the World Health Organization: below 18.5 is Underweight, 18.5–24.9 is Normal weight, 25–29.9 is Overweight, and 30 or above is Obese. These thresholds apply to most adults.
Is BMI accurate?: BMI is a useful population-level screening tool but has limitations for individuals. It does not account for muscle mass, bone density, age, sex, or body fat distribution. Athletes may have a high BMI despite low body fat. Always consult a healthcare professional for a full assessment.
How is BMI calculated in imperial units?: For pounds and inches: BMI = (weight in lbs × 703) ÷ height in inches². This calculator converts your feet and inches to centimetres and your pounds to kilograms before applying the standard formula.
What is my healthy weight range?: The healthy weight range shown below your result is the weight at which your BMI would be between 18.5 and 24.9 for your specific height. It gives you a practical target range rather than a single number.
Is this calculator private?: Yes. All calculations happen inside your browser using JavaScript. Your height and weight are never sent to any server, stored, or shared with anyone.

From the blog

BMI Calculator: How to Calculate Body Mass Index and What It Means A practical guide to BMI — the formula, healthy ranges, limitations, and how to use the calculator for metric and imperial units. Read the post →