Enter Your Details
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese | 30 and above |
Enter your height and weight,
then click Calculate BMI
What Is BMI?
Body Mass Index (BMI) is a simple numerical value derived from your weight and height. It's the most widely used screening tool by doctors, nutritionists, and health organisations worldwide to assess whether a person's weight falls within a healthy range for their stature.
Our free BMI calculator supports both metric (kilograms and centimetres) and imperial (pounds, feet and inches) input systems. After calculating, you'll see your exact BMI value, your weight category, a visual gauge, and the healthy weight range for your specific height.
BMI Categories (WHO Standard)
- Below 18.5 — Underweight
- 18.5 – 24.9 — Normal weight
- 25 – 29.9 — Overweight
- 30 – 34.9 — Obese Class I
- 35 – 39.9 — Obese Class II
- 40 and above — Obese Class III (Severe)
BMI is a population-level screening indicator, not a diagnostic tool. Athletes with high muscle mass, elderly people with muscle loss, and pregnant women may get misleading readings. Always consult a healthcare professional for a full assessment.
How to Use the BMI Calculator
The Formulas
Metric: BMI = weight(kg) ÷ height²(m²)
Imperial: BMI = 703 × weight(lbs) ÷ height²(in²)
The ideal weight shown uses the Devine formula, a widely-used clinical estimate: 50 kg + 2.3 kg per inch over 5ft for men, 45.5 kg + 2.3 kg per inch over 5ft for women, with a ±5 kg range shown.
Behind the Scenes
Everything runs in your browser — no data is sent to any server. The calculations are pure JavaScript using the standard WHO/CDC formulas.
The BMI gauge maps the BMI range 10–45 to a 0–100% position on the track, then uses CSS transitions to animate the needle smoothly on each calculation.
The healthy weight range is back-calculated from BMI 18.5 and 24.9 for your entered height: min weight = 18.5 × height(m)² and max weight = 24.9 × height(m)².
For imperial display, weights are converted from kg using the factor 1 kg = 2.2046 lbs, rounded to one decimal place.
The Devine ideal weight formula was created by B.J. Devine in 1974 and remains one of the most cited clinical estimates despite newer alternatives. We use it for its wide recognition, not as a strict target.
Use Cases
- Personal health tracking — Check your BMI periodically to track progress during a diet or fitness programme.
- Goal setting — Use the healthy weight range to set realistic target weights before starting a weight-loss journey.
- Healthcare screening — Nurses and doctors use BMI as a quick initial screen in clinical consultations.
- Fitness coaching — Personal trainers use BMI alongside body fat % and waist circumference to give clients a fuller picture.
- Insurance and research — BMI is frequently used in health insurance risk assessments and epidemiological studies.
- Education — Students studying nutrition, public health, or medicine often use BMI calculators for coursework.
Remember: BMI is one data point among many. Combining it with waist circumference, body fat percentage, blood pressure, and other health markers gives a much more complete picture of overall health.