Use this BMI calculator to estimate your body mass index from your height and weight. Enter your measurements in metric or imperial units to get your BMI result and see the corresponding adult BMI category.
BMI is a quick screening measure that compares weight with height. It can be useful for starting a conversation about general health, but it is not a diagnosis and does not measure body fat directly.
How to use the BMI Calculator
- Select metric or imperial units.
- Enter your height and weight as accurately as possible.
- Select Calculate to see your BMI result.
- Read the category and important limitations below before drawing conclusions from the number.
For the most useful result, measure your height without shoes and use a recent weight measurement.
BMI calculation example
Suppose an adult is 170 cm tall and weighs 70 kg.
Their BMI is calculated as:
BMI = weight in kilograms / height in metres squared
BMI = 70 / (1.70 x 1.70)
BMI = 24.2
A BMI of 24.2 falls within the adult healthy weight category range.
What does BMI mean
Body mass index is a number calculated from weight relative to height. For adults aged 20 and older, commonly used BMI categories are:
- Underweight: below 18.5
- Healthy weight: 18.5 to less than 25
- Overweight: 25 to less than 30
- Obesity: 30 or higher
The obesity category is sometimes divided into additional classes for clinical and public-health reporting. Your calculator result should present the number first and use respectful, person-first language when showing any category.
BMI formula
For metric measurements:
BMI = weight in kilograms / height in metres squared
For imperial measurements:
BMI = 703 x weight in pounds / height in inches squared
Both formulas produce the same BMI value when the measurements are entered correctly.
Why BMI has limits
BMI is one health screening measure, not a full picture of health. It does not directly measure body fat, body composition, fitness, diet, medical history, or blood pressure.
For example, a person with more muscle may have a higher BMI without having a high level of body fat. BMI may also be less useful on its own for children and teenagers, pregnant people, older adults, athletes, and people with certain health conditions.
A BMI category should not be used to diagnose a disease or make treatment decisions. If you have concerns about your weight, nutrition, physical activity, or health, speak with a qualified healthcare professional.
Adult BMI and children or teens
This calculator is intended for adults aged 20 and older.
BMI is interpreted differently for children and teenagers because age and sex are considered when determining BMI percentile. Do not use adult BMI categories to assess a child or teen.
Frequently asked questions
For adults aged 20 and older, the standard categories on this page apply at any age: 18.5 to 25 is the
healthy range. BMI isn’t age-adjusted for adults, though body composition naturally shifts with age one
more reason the page stresses that BMI is a screening measure, not a verdict. For children and teens, age
and sex percentiles are used instead, so don’t apply adult cutoffs to them.
The formula and categories are the same for adult men and women. In practice, women typically carry a higher
body-fat percentage at the same BMI than men do another reason two people with identical BMI numbers can
have different health pictures. The calculator doesn’t ask for sex; it applies the standard adult formula
to everyone.
BMI falls when weight drops relative to height. The sustainable levers are regular movement, balanced eating,
enough sleep, and consistency over months not crash diets. Aim for gradual change and re-check monthly
rather than daily. And since BMI is only one indicator, consider talking with a healthcare professional about
a plan that fits you.
Waist circumference and waist-to-height ratio catch abdominal fat that BMI misses, while trends in how your
clothes fit, your energy levels, and your blood pressure tell their own story. Many people use BMI as the
quick number and a waist measurement as the reality check. No single figure captures health that’s exactly
why the page lists BMI’s limits.
No. Like every tool on ToolsByMeh, it runs entirely in your browser your height and weight are never sent
to a server, stored, or tied to an account. There are no sign-ups. Refresh the page and your entries are
gone.
Important health notice
This tool is for educational and informational purposes only. It does not provide medical advice, diagnosis, or treatment.
BMI is only one possible health indicator. A healthcare professional can consider BMI alongside medical history, health behaviours, physical examination findings, and other relevant factors.
You may also find the Unit Converter useful for changing between metric and imperial measurements, or use the Age Calculator for everyday date calculations.
Curious what a specific height and weight means?
Read our guide: 100 Pounds and 5’4″, What Does This Mean for Your Health?
Reviewed by ToolsByMeh
Last reviewed: September 21, 2026
Methodology: BMI is calculated using height and weight with the standard metric or imperial formula.