BMI Calculator
Check your Body Mass Index in seconds.
Body Mass Index estimates body fat from height and weight using the formula weight ÷ height².
BMI does not account for muscle mass, bone density, or body composition. If you are tracking fitness over time, consistent measurements matter more than any single number.
How to use
- Choose metric or imperial units.
- Enter your height and weight, then click Calculate.
- Compare your result with the healthy range shown.
About this tool
Adults fall into four standard categories: underweight (below 18.5), healthy (18.5–24.9), overweight (25–29.9) and obesity (30+).
BMI is a rough screening tool — athletes with high muscle mass can score as "overweight" while being very fit.
How it works
Body Mass Index is weight divided by height squared: BMI = kg / m^2. Because height is squared, small differences in height change the result more than you might expect — which is why the formula uses meters, not centimeters.
In imperial units the same relationship is written as BMI = 703 x lb / in^2. The 703 is just a conversion constant; both versions give the same number. This calculator converts imperial inputs to metric first, then applies the standard formula.
Worked examples
170 cm, 65 kg: Convert height to meters: 1.70 m. Square it: 1.70 x 1.70 = 2.89. Divide weight: 65 / 2.89 = 22.5. That falls in the healthy range (18.5-24.9).
5 ft 7 in, 150 lb: Height in inches: 67. Weight in the imperial formula: 703 x 150 / (67 x 67) = 105450 / 4489 = 23.5. Also in the healthy range.
Quick reference
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 - 24.9 | Healthy weight |
| 25.0 - 29.9 | Overweight |
| 30.0 and above | Obesity |
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9 is considered the healthy range.
Is BMI accurate for everyone?
Not entirely — it does not distinguish muscle from fat, so very muscular people, the elderly and pregnant women should interpret it cautiously.
Is my data stored?
No. Your height and weight never leave your browser.
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