Free BMI Calculator Online
A free BMI calculator computes your Body Mass Index from height and weight instantly. Switch between metric (kg/cm) and imperial (lb/ft) — no signup, results appear in your browser immediately.
Enter your height and weight to calculate BMI and see your category (underweight, normal, overweight, obese). Toggle between metric and imperial units. For general fitness awareness only — not medical advice. Free, no signup, runs locally.
Your BMI
NaN
Obese
For general awareness only — not medical advice.
Runs 100% in your browser. Your data never leaves your device.
Standard BMI formula (weight ÷ height²) implemented in JavaScript — calculations run entirely on your device.
How to Use BMI Calculator
- Choose metric (kg, cm) or imperial (lb, ft/in) units
- Enter your height and weight
- Your BMI and category display instantly
- Adjust values anytime to compare different measurements
When Would You Use This?
Gym members tracking progress often recalculate BMI monthly alongside weight — quicker than searching through health apps with ads and account prompts.
Travelers switching between countries think in pounds one week and kilograms the next — toggling units avoids manual conversion mistakes.
BMI is a screening tool, not a diagnosis. Athletes with high muscle mass may show 'overweight' despite low body fat — use it as one data point, not the whole picture.
Frequently Asked Questions
- Is this BMI calculator free to use?
- Yes, completely free. No signup, no login, no payment ever.
- Do I need to create an account?
- No account needed. Open the tool and start using it immediately.
- Is my data safe?
- Everything runs in your browser. Your height and weight are never uploaded to our servers.
- Is BMI accurate for everyone?
- BMI is a general screening tool. It may not reflect body composition for athletes, elderly people, or those with high muscle mass. Consult a healthcare provider for personal advice.