BMI screening
Calculate your BMI online with correct measurements
The BMI calculator gives you an instant result in metric or imperial units, with the category and honest guidance about what the number can and cannot tell you.
Measure and calculate correctly
Accurate inputs are the entire game.
Measure height barefoot
Stand straight against a wall and measure without shoes, ideally at the same time of day.
Weigh consistently
Weigh yourself at the same time of day, preferably in the morning after using the bathroom.
Enter the values
Open the BMI calculator and enter height and weight in either unit system.
Read the category
Check the result and the range it falls into, then track the trend over weeks rather than days.
Ways to check your BMI
The method matters less than the measurement quality.
Online calculator
The BMI calculator computes the value and category instantly, in your browser, with no account.
Best for quick, private checksManual formula
BMI equals kilograms divided by meters squared, or 703 times pounds divided by inches squared. Works anywhere but invites arithmetic errors.
Best when you enjoy the mathProfessional measurement
Clinics measure height and weight precisely and combine BMI with waist, blood work, and history.
Best for medical decisionsThe standard ranges
For adults, BMI below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 and above is obese. The boundaries are screening cutoffs, not verdicts; health risk changes gradually across them.
Honest limitations
BMI does not measure body composition. Muscular people can show overweight with low body fat, and older adults can show normal BMI with low muscle mass. The number is most useful as a screening signal combined with waist circumference, activity, and professional advice.
Children, teenagers, and pregnant people need age- and sex-adjusted references, not the adult ranges. If you fall into one of those groups, ask a healthcare provider rather than relying on a general calculator.
Jump to tool
Check your BMI now
Open the BMI calculator, enter your height and weight, and see your category instantly. Free, private, and local.
Open BMI CalculatorWhy BMI checks go wrong
- Height measured with shoes or estimated adds real error
- Weighing after meals and later in the day skews results
- Converting units by hand invites mistakes
- Reading category boundaries as medical diagnoses
Healthy tracking practices
- Measure at the same time of day each week
- Record the date with each result to see the trend
- Combine BMI with waist circumference for context
- Discuss results with a professional before acting on them
Frequently asked questions
Is the metric or imperial formula different?
The result is the same; only the arithmetic differs. Metric uses kilograms divided by meters squared, imperial uses 703 times pounds divided by inches squared. The calculator handles both.
What does a BMI of 25.2 mean?
It falls in the overweight range, but the boundary is a convenience cutoff, not a cliff. Read it as a signal to look at trends and other measures, not as a diagnosis.
Why does my BMI say overweight when I am athletic?
BMI cannot distinguish muscle from fat. If you have high muscle mass, a BMI above 25 can be normal for your body; waist circumference and body-fat measurement give a better picture.
Is my health data stored when I calculate?
No. The BMI calculator runs entirely in your browser. Your height and weight are processed locally and never sent to or stored on a server.
Private health calculation
The BMI calculator processes your measurements locally in your browser. No health data is uploaded, stored, or shared, making it safe for sensitive use.
Open BMI Calculator