Free BMI Calculator
Calculate your Body Mass Index.
What is the BMI Calculator?
Body Mass Index is a quick way to see whether your weight sits in a healthy range for your height. Doctors and health services use it as a first-glance screening number because it's simple to calculate and easy to compare over time.
This calculator works out your BMI from your height and weight in either metric or imperial units, and tells you which standard category the result falls into. It's a starting point for a conversation with a professional, not a diagnosis.
Last updated: Aug 12, 2026
What does this tool do?
You enter your height and weight, and the tool divides your weight by the square of your height to produce a single BMI number.
It then places that number in the standard adult categories — underweight, healthy weight, overweight, or obese — so you can see where you stand at a glance.
Key features
Metric and imperial
Enter centimeters and kilograms or feet, inches, and pounds.
Instant category
See which standard weight range your BMI falls into.
Clear number
Get a precise BMI value, not just a band.
No account
Use it right away with nothing to sign up for.
Private
Your measurements are calculated in the browser and never stored.
Example
Common use cases
- People tracking health — Check where your weight sits and watch the trend over time.
- Dieters — Set a realistic target range before starting a plan.
- Fitness beginners — Get a baseline number to measure progress against.
- Parents — Understand adult BMI categories (children use separate charts).
- Nurses and clinics — Do a fast screening calculation during intake.
- Insurance applicants — See the number a form is likely to ask for.
- Coaches — Give clients a simple reference point alongside other measures.
- Students — Learn how the BMI formula works with real numbers.
Benefits
- It's a fast, standardized screening number you can track over time.
- It works in both metric and imperial without converting first.
- It gives context by showing the category, not just the value.
- Your measurements stay on your device.
Tips
- Measure weight at the same time of day for consistent tracking.
- BMI is a screening tool, not a diagnosis — discuss results with a professional.
- Very muscular people can read as overweight because muscle is dense.
- BMI categories are for adults; children and teens use age-specific charts.
- Pair BMI with waist measurement for a fuller picture of health.
- Track the trend rather than fixating on a single reading.
- Round measurements consistently so comparisons are fair.
- A healthy adult BMI is generally 18.5 to 24.9.
Common mistakes to avoid
Treating BMI as a diagnosis
Fix: Use it as a screening number and follow up with a healthcare professional.
Applying adult BMI to children
Fix: Children and teens use age- and sex-specific percentile charts instead.
Ignoring body composition
Fix: Remember that athletes and very muscular people can read high without excess fat.
Mixing up units
Fix: Keep height and weight in the same system — metric or imperial — before calculating.
How it works
- 1
Enter height & weight
Use metric or imperial units.
- 2
Get your BMI
See your BMI and category instantly.
Frequently asked questions
A BMI between 18.5 and 24.9 is considered a healthy weight for most adults.
BMI is a useful general guide but doesn't account for muscle mass, so athletes may read high.
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight and 25 or above is overweight.
It's your weight in kilograms divided by your height in meters squared. The tool handles imperial units for you.
It's a useful general guide but doesn't account for muscle mass, bone density, or fat distribution, so it can misclassify some people.
No. Children and teenagers should use age- and sex-specific BMI-for-age charts, not the adult categories.
No. The calculation runs in your browser and nothing is saved or uploaded.
BMI can't tell muscle from fat. Very muscular people often read high despite low body fat.
Conclusion
BMI is a simple first look at whether your weight fits your height, best used as one signal among several. Check it alongside the body-fat and ideal-weight calculators for a rounder view, and talk to a professional about what the numbers mean for you.