Free BMI Calculator
Work out your Body Mass Index from height and weight — no signup, nothing sent to a server.
BMI
—
Category
—
How to calculate BMI
-
1
Choose your unit system
Pick Metric (cm/kg) or Imperial (ft-in/lb).
-
2
Enter height and weight
Type your current height and weight into the fields.
-
3
Read your BMI and category
Your BMI value and weight category update instantly as you type.
Example use cases
General health screening
Get a quick sense of where your weight falls relative to standard BMI ranges.
Tracking change over time
Recalculate periodically to see how BMI shifts alongside a fitness or diet plan.
Doctor or insurance forms
Quickly work out a BMI figure some forms ask for directly.
Frequently asked questions
How is BMI calculated?
BMI = weight in kilograms ÷ (height in metres)². For imperial units, BMI = 703 × weight in pounds ÷ (height in inches)².
What do the BMI categories mean?
Under 18.5 is classed as underweight, 18.5–24.9 as normal weight, 25–29.9 as overweight, and 30 or above as obese, per WHO adult BMI ranges.
Is BMI accurate for everyone?
BMI is a simple screening measure and doesn't distinguish muscle from fat, so it can be less accurate for athletes, older adults, pregnant people, or children. It's a starting point, not a diagnosis.
Is my height and weight sent to a server?
No. The calculation runs entirely in your browser — nothing is transmitted or logged.