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Free BMI Calculator Online

Free BMI Calculator Online is a free online tool by US AI. Body mass index. It runs completely in your browser — no signup, no download, works on mobile and desktop.

▶ Use Free BMI Calculator Now — Free

📊 BMI categories chart

BMI rangeCategory
Below 18.5Underweight
18.5 – 24.9Normal (healthy range)
25.0 – 29.9Overweight
30.0 and aboveObese

These are the standard WHO adult BMI ranges. BMI is a screening tool, not a diagnosis — check with your doctor.

📖 How to use

  1. Open the tool with the button above — it loads instantly.
  2. Enter your height in cm and weight in kg, press Calculate — your BMI plus health category (Underweight, Normal, Overweight or Obese) appears instantly.
  3. Your health numbers stay on this device — nothing is uploaded or shared. Estimates only — not medical advice.

✨ Why use this tool?

US AI's free bmi calculator online is fast, private and 100% free forever. Bookmark this page and share it with anyone who needs it.

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❓ Frequently Asked Questions

What is a good BMI?

A BMI between 18.5 and 24.9 is considered the healthy range for most adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.

How is BMI calculated?

In metric units, divide your weight in kilograms by the square of your height in meters (kg ÷ m²). In imperial units, divide your weight in pounds by the square of your height in inches, then multiply by 703.

Is BMI accurate for everyone?

Not always. BMI doesn't distinguish muscle from fat, so athletes, bodybuilders, pregnant women and the elderly can get misleading results. It's a screening tool — a doctor can give you a fuller picture.

What should I do if my BMI is high?

Don't panic — one number doesn't define your health. Consider talking to a doctor or dietitian about diet, exercise and sleep, and track your progress over time rather than chasing a single reading.