BMI Calculator
Free BMI Calculator — find your Body Mass Index, category (underweight, healthy, overweight, obese) and healthy weight range. Metric and Imperial units.
BMI Calculator — Calculate Your Body Mass Index Instantly
Body Mass Index (BMI) is a quick, widely used measure of body weight relative to height. While not perfect, it's a useful first indicator of whether you're underweight, healthy, overweight, or obese. Our BMI Calculator gives you the BMI value, the WHO category you fall in, and the healthy weight range for your height.
Enter height and weight in metric or imperial units. Get your BMI, healthy weight range, and clear interpretation. No signup, no cost.
How to Calculate BMI
1. Enter Height
Type your height in centimetres or feet/inches. The calculator handles both.
2. Enter Weight
Type your weight in kilograms or pounds. Use a recent measurement for best accuracy.
3. Calculate
Press Calculate. BMI = weight (kg) ÷ height (m)², or 703 × weight (lb) ÷ height (in)² in imperial units.
4. View Category
See your BMI value, category (underweight/healthy/overweight/obese), and ideal weight range.
BMI Calculator Features
WHO Categories
Your BMI is placed in the WHO adult categories: underweight below 18.5, healthy 18.5–24.9, overweight 25–29.9 and obese 30 or more.
Metric and Imperial
Use kilograms and centimetres, or pounds with feet and inches. Each tab has its own formula, so there is nothing to convert by hand.
Healthy Weight Range
See the weight range that puts you in the healthy BMI category given your height.
Visual Indicator
Coloured bar shows where your BMI falls on the spectrum — green for healthy, yellow/red otherwise.
Mobile-Friendly
Optimised for phones — check your BMI on the go without opening any app.
Free and Private
No signup, no tracking. Runs entirely in your browser.
How BMI Is Calculated
In metric units, BMI = weight (kg) ÷ height (m)²; in imperial units, BMI = 703 × weight (lb) ÷ height (in)², with feet and inches added up to inches first. The result is rounded to two decimal places. The healthy weight range for your height is the weight that gives a BMI of 18.5 to 24.9: 18.5 × height² to 24.9 × height² (divided by 703 in imperial units).
The BMI is then placed in the WHO adult categories, judged on the exact value before rounding: below 18.5 underweight, from 18.5 up to 25 healthy, from 25 up to 30 overweight, and 30 or more obese. Age (optional), gender and activity level are shown with your result but don’t change the BMI; for an age under 20, the result notes that adult categories don’t apply.
Worked examples:
- 70 kg and 175 cm: 70 ÷ 1.75² = 22.86, a healthy weight; the healthy range for 175 cm is 56.7 – 76.3 kg.
- 154 lb and 5 ft 9 in (69 in): 703 × 154 ÷ 69² = 22.74, a healthy weight; the healthy range is 125.3 – 168.6 lb.