BMI Calculator
Find your body mass index (BMI), its weight category and the healthy weight range for your height.
How to use the BMI Calculator
- Choose the units.
- Enter the height – feet.
- Enter the height – inches.
- Enter the height.
- Enter the weight.
- Enter the weight.
- Press Calculate. The result updates automatically as you type.
About the BMI Calculator
Body mass index compares your weight to your height and is the quickest screening number doctors use to flag possible underweight or excess weight. Because it needs only two measurements, it is useful for tracking trends over time and for comparing large groups of people.
BMI does not measure body fat directly. Muscular athletes can score as "overweight" while carrying little fat, and older adults may have a normal BMI with low muscle mass. Pair BMI with your waist measurement or a body fat estimate for a fuller picture.
Results are estimates for general information only and are not medical advice. Talk to a doctor or registered dietitian before making major changes.
Formula
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²
The 703 factor converts pounds and inches to the metric result. BMI Prime is BMI ÷ 25 (the upper limit of the healthy range), so a value above 1.0 means overweight. The ponderal index divides weight by height cubed and is less sensitive to very tall or short stature.
| BMI | Category (adults) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity class I |
| 35 – 39.9 | Obesity class II |
| 40 and above | Obesity class III |
Example calculation
Using the default values:
- Units = US (ft, in, lb)
- Height – feet = 5 ft
- Height – inches = 10 in
- Weight = 170 lb
the calculator returns:
- BMI: 24.4 kg/m²
- Category: Healthy weight
- Healthy weight for your height: 128.9 – 173.5 lb
- To reach a healthy BMI: You are already in the healthy range
- BMI Prime: 0.98
- Ponderal index: 13.7 kg/m³
Frequently asked questions
What is a healthy BMI?
For most adults a BMI from 18.5 to 24.9 is considered a healthy weight. Some health agencies use lower cut-offs (around 23) for people of Asian descent because health risks rise at lower BMIs.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. A 5 ft 10 in (70 in) person weighing 170 lb has a BMI of 170 × 703 ÷ 4,900 ≈ 24.4.
Is BMI accurate for muscular people?
Not very. BMI cannot tell muscle from fat, so lean, muscular people often get a higher BMI than their body fat suggests. A body fat test gives a better picture.
Does BMI work for children?
Children and teens use BMI-for-age percentiles rather than the adult categories, because healthy body composition changes as they grow.
Last updated: · Category: Health & Fitness calculators