⚖️BMI Calculator
Calculate your body mass index in metric or imperial units. See your WHO weight category and healthy weight range instantly.
This tool is a general reference and is not medical or dietary advice. Please consult a registered dietitian or physician before making any significant change to your diet, nutrition, or weight. Individual needs vary, and only a qualified professional can give advice tailored to you.
Free BMI Calculator Online
Want to check your BMI in seconds? Our free BMI Calculator gives you your body mass index the moment you enter your height and weight. As a fast and reliable bmi calculator, it works in both metric and imperial units and instantly shows your BMI value along with the standard World Health Organization weight category—so you get a clear, simple result without the math.
But it does more than a single number. See the healthy-weight range for your specific height, so you know what BMI band you fall into and what range is generally considered healthy. BMI is a quick screening figure, not a full picture of health, and the tool explains what it does and doesn't tell you.
Simply enter your height and weight to see your result instantly. No sign-up, no downloads, no limits—just a clear, private calculation whenever you need it. Learn more in the About and FAQ sections below.
About the BMI Calculator
Key features
Metric & imperial input
Switch between metric (cm, kg) and imperial (ft/in, lb) at any time. The result updates instantly in either mode, and the healthy weight range is shown in whichever unit you've selected.
BMI value & WHO category
Your BMI is displayed to one decimal place alongside the WHO weight category — underweight, healthy weight, overweight, or obese — with a colour-coded badge so the category is immediately clear.
Healthy weight range for your height
The tool calculates the minimum (BMI 18.5) and maximum (BMI 25) weight that falls in the healthy range for your specific height, shown in your chosen unit alongside your result.
Visual BMI scale
A colour-banded scale bar positions your result across the four WHO ranges — underweight, healthy, overweight, and obese — so you can see at a glance where you sit relative to each boundary.
How BMI is calculated
Metric formula
BMI = weight (kg) ÷ height (m)². Height in centimetres is divided by 100 to convert to metres before squaring.
Imperial formula
BMI = 703 × weight (lb) ÷ height (in)². Feet and inches are combined into total inches. The two formulas produce identical results.
WHO boundaries
Underweight: below 18.5. Healthy weight: 18.5–24.9. Overweight: 25–29.9. Obese: 30 and above.
Healthy weight range
Minimum = 18.5 × height (m)². Maximum = 25 × height (m)². These are the weights at which BMI hits 18.5 and 25 for your specific height.
A note on BMI's limitations
Frequently Asked Questions
How does the BMI calculator work?
Enter your height and weight in either metric or imperial units and the tool instantly calculates your body mass index and shows which standard weight category it falls into — no button refresh needed.
Is this BMI calculator free to use?
Yes, it's completely free with no sign-up, downloads, or limits. Use it as often as you like.
What is BMI?
Body mass index (BMI) is a number calculated from your height and weight that's used as a quick, general screening measure to categorise weight ranges in adults.
How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). The calculator handles the conversion automatically whether you enter metric or imperial values.
What are the BMI categories?
This tool uses the standard World Health Organization adult ranges: underweight (BMI below 18.5), healthy weight (18.5 to 24.9), overweight (25 to 29.9), and obese (30 and above). The tool shows which band your result falls into.
Can I use feet/inches and pounds?
Yes. You can switch between metric (cm, kg) and imperial (ft/in, lb) units, and the result updates instantly.
Does it show a healthy weight range for my height?
Yes. Alongside your BMI, it shows the weight range generally considered healthy for your specific height — the minimum weight at BMI 18.5 and the maximum at BMI 25.
Is BMI an accurate measure of health?
BMI is a useful quick screening tool, but it has limits — it doesn't distinguish muscle from fat or account for age, sex, ethnicity, or body composition. It's a general indicator, not a diagnosis.
Is my data stored anywhere?
No. Your height and weight are processed directly in your browser and are never stored or sent to a server, keeping your information completely private.
Should I make health decisions based on my BMI?
No — BMI is just one general indicator. For personalised advice about your weight or health, speak to a doctor or qualified health professional rather than relying on a single number.