Online Tool Store
BMI Calculator
Calculate BMI in metric or imperial units, see your WHO/CDC weight category including obesity Class I–III, and your healthy weight range instantly.
This works right here on your device — nothing gets sent out.
Example shown — replace it with your own numbers.
How the BMI calculator works
- Choose metric or imperial units, then enter your height and weight.
- Your BMI and WHO/CDC weight category — including obesity Class I, II, or III — update as you type, with your exact position marked on the scale below.
- The healthy weight range for your height (BMI 18.5–24.9) is calculated alongside it.
- Use "Copy result" to copy your BMI, category, and healthy range as text.
The formula
BMI is weight divided by height squared:
BMI = weight (kg) / height (m)²
Example: a person who is 170 cm (1.70 m) tall and weighs 68 kg has a BMI of 68 / 1.70² = 68 / 2.89 ≈ 23.5, in the normal range. In imperial units the same formula is BMI = 703 × weight (lb) / height (in)². Weight categories follow the WHO/CDC classification: underweight is below 18.5, normal is 18.5–24.9, overweight is 25–29.9, and obese is 30 and above — split into Class I (30–34.9), Class II (35–39.9), and Class III (40 and above). BMI is a screening measure, not a diagnosis — it doesn't distinguish muscle from fat and doesn't account for age, sex, or build. Talk to a healthcare professional for a full assessment.
FAQ
How do I calculate my BMI?
Divide your weight in kilograms by your height in metres squared: BMI = kg ÷ m². In imperial units, BMI = 703 × weight (lb) ÷ height (in)². This calculator does the maths for you the moment you enter your height and weight.
How do I calculate my BMI ranges?
A healthy-weight range is the span of weights, for your exact height, where BMI falls between 18.5 and 24.9. This calculator solves that automatically and shows it under "Healthy weight range" in whichever unit you’re using.
What is the correct BMI for my age?
For adults 20 and over, the WHO/CDC categories (underweight, normal, overweight, obese) are the same at every age — there is no separate "correct" range by age. The CDC notes that older adults tend to carry more body fat than younger adults at the same BMI, so a healthcare provider may factor that in. Children and teens (2–19) are assessed with age- and sex-specific BMI percentiles instead, which this calculator does not cover.
What is the BMI of 70 kg and 170 cm?
70 kg at 170 cm (1.70 m) gives a BMI of 70 ÷ 1.70² = 70 ÷ 2.89 ≈ 24.2, which is in the normal-weight range (18.5–24.9).
Is my BMI or my data sent anywhere?
No. Every calculation runs locally in your browser using JavaScript — nothing you type is uploaded to Online Tool Store or anywhere else.
How we compare
| Feature | Online Tool Store | Calculator.net | CDC Adult BMI Calculator | NIH/NHLBI BMI Calculator |
|---|---|---|---|---|
| Obesity split into Class I / II / III | ✓ | Yes, in a 7-tier WHO table | Yes, 3 classes | No — single "obese" result |
| Your exact BMI marked on a visual scale | ✓ | Yes, a chart image | No — text result only | No — text result only |
| One-click copy of your result | ✓ | No — print or save-as-image only | No — print only | No — print/share only |
| Metric and imperial in one page | ✓ | ✓ | ✓ | ✓ |
Choose Calculator.net for extras like BMI Prime, Ponderal Index, or children's percentile charts. Choose the CDC or NIH/NHLBI calculators for official U.S. government guidance and health resources. Choose Online Tool Store when you want your exact BMI marked on a scale with obesity subclasses and a one-click copy of your result, calculated locally with no ads or extra pages.