Online BMI Calculator – Free Body Mass Index Tool
Use this online BMI calculator to check your body mass index instantly. Enter your height and weight, and see if you’re in the underweight, normal, overweight, or obese range. Works with US units (feet, inches, pounds) or metric. No sign‑up required.
Enter your details and click calculate.
How to Use This Online BMI Calculator
This free online BMI calculator is simple: pick your unit system (US or metric), enter your height and weight, and click calculate. You’ll get your BMI number and see where you fall on the standard weight categories. The tool also shows a color‑coded gauge and reference chart so you can understand your result at a glance.
What Is BMI?
BMI, or body mass index, is a number calculated from your height and weight. It’s a quick screening tool used to identify possible weight problems in adults. While it doesn’t measure body fat directly, it gives a reliable snapshot that works for most people.
- Underweight: BMI below 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25.0 – 29.9
- Obese: BMI 30.0 and above
Why Use This BMI Calculator?
- No registration. It’s a free online BMI calculator no sign up required.
- US and metric units. Works with BMI calculator in pounds and inches or centimeters and kilograms.
- Instant results. One click and you see your BMI plus a visual gauge.
- Private and secure. All calculations happen in your browser. Nothing is stored or sent anywhere.
- Works on any device. Phone, tablet, or computer.
Step by Step
- Choose your unit system. Select US (pounds, feet/inches) or metric.
- Enter your height and weight. Type your numbers carefully.
- Click "Calculate My BMI". Your BMI and weight category appear instantly.
BMI Chart for Adults
| Underweight | Below 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese Class I | 30.0 – 34.9 |
| Obese Class II | 35.0 – 39.9 |
| Extreme Obesity | 40.0+ |
Frequently Asked Questions
Q: How do I calculate my BMI online?
A: Just enter your height and weight above. The calculator uses the standard formula: weight (lbs) ÷ height (inches)² × 703 for US units, or weight (kg) ÷ height (m)² for metric.
Q: Is this BMI calculator free?
A: Yes. It’s a 100% free BMI calculator. No sign‑up, no fees.
Q: Can I use this for men and women?
A: Yes. This BMI calculator for men and women uses the same standard adult categories. BMI does not change by gender.
Q: Does BMI measure body fat?
A: No, BMI is an indirect estimate. It doesn’t separate muscle from fat. Athletes with a lot of muscle may have a high BMI but low body fat.
Q: Is my information stored?
A: Never. All math is done in your browser. Nothing is uploaded or saved.
