BMI Calculator: Check Your Body Mass Index & Healthy Weight
Find your Body Mass Index (BMI), weight category, and healthy weight range in seconds. Switch between metric (cm, kg) and US/imperial (ft, in, lb) units anytime. It is free, private, and needs no signup.
BMI categories for your height
| Category | BMI range (kg/m²) | Weight for your height |
|---|
This calculator is an informational screening tool for non-pregnant adults aged 20 and older. It does not measure body fat directly or account for muscle mass, bone structure, age, or sex, and it is not medical advice. Speak with a qualified healthcare professional before making changes to your diet or exercise plan.
How to Use the BMI Calculator
Pick your units
Choose Metric (centimeters and kilograms) or Imperial (feet, inches, and pounds). You can switch anytime.
Enter height and weight
Type your measurements or drag the sliders. Your BMI and position on the scale update right away.
Check your healthy weight range
See the weight range that matches a healthy BMI for your exact height, plus every category in the table below.
Everything You Need to Understand Your BMI
Metric & Imperial
Switch between cm/kg and ft/in/lb in one click, with instant conversion of your numbers.
Healthy weight range
See the exact minimum and maximum healthy weight for your height, not just a single number.
Clear weight goal
Find out right away if you are in the healthy range, or how much weight to lose or gain to reach it.
WHO & Asian scales
Check your score against standard World Health Organization cutoffs or Asian and Indian health cutoffs.
BMI Prime & Ponderal Index
Includes Ponderal Index for very tall or short adults and BMI Prime for quick comparison.
Private by design
Everything runs inside your browser. Your height and weight are never uploaded or saved anywhere.
What Is Body Mass Index (BMI)?
Body Mass Index (BMI) is a simple number worked out from your height and weight. Doctors, health agencies, and fitness professionals around the world use it as a quick starting point to check whether an adult's weight falls into the underweight, healthy weight, overweight, or obesity range. While BMI does not measure body fat directly, research shows that it tracks closely with health risks linked to extra body weight across large groups of adults.
The BMI Formula
You can work out BMI in either metric or imperial units:
- Metric formula: BMI = weight (kg) ÷ [height (m)]2
- US / Imperial formula: BMI = 703 × weight (lb) ÷ [height (in)]2
Metric example. You are 170 cm (1.70 m) tall and weigh 65 kg. Multiply 1.70 by 1.70 to get 2.89. Divide 65 by 2.89 and you get a BMI of about 22.5, which sits comfortably inside the healthy weight range.
Imperial example. You are 5 feet 7 inches (67 inches) tall and weigh 150 lb. Multiply 67 by 67 to get 4,489. Multiply 703 by 150 to get 105,450, then divide by 4,489 to get a BMI of about 23.5.
Adult BMI Categories (WHO & Asian Guidelines)
Under the standard World Health Organization (WHO) and US CDC guidelines for adults aged 20 and older, a BMI below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25.0 to 29.9 is overweight, and 30.0 or higher falls into obesity (split into Class I from 30.0 to 34.9, Class II from 35.0 to 39.9, and Class III at 40.0 or above).
For people of South Asian and East Asian heritage, health organizations often recommend lower cutoffs—18.5 to 22.9 for a healthy weight, 23.0 to 24.9 for overweight, and 25.0 or higher for obesity—because metabolic risks such as type 2 diabetes and high blood pressure can appear at lower BMI values. You can switch between both scales at the top of the calculator.
Limitations of BMI & Other Helpful Measures
- Muscle vs. fat. Muscle is dense and heavy. Athletes and people who lift weights often have an overweight BMI even when their body fat is low.
- Age and bone structure. Older adults can lose muscle over time, meaning their BMI may look normal even if they carry higher body fat.
- Very tall or short height. Because the standard formula squares height instead of cubing it, very tall people can get a slightly high BMI reading and very short people can get a slightly low reading. That is why this calculator also displays your Ponderal Index (weight divided by height cubed), where 11 to 15 kg/m³ is considered typical.
- Waist size matters too. Carrying weight around the waist raises health risks more than carrying weight on the hips or thighs. Checking waist circumference alongside BMI gives a clearer picture.
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Frequently Asked Questions
Is this BMI calculator free?
Yes. The BixTools BMI calculator is completely free to use, with no signup and no limits.
What does BMI mean?
BMI stands for Body Mass Index. It is a number calculated from your height and weight that health organizations use to group adult weight into categories such as underweight, healthy weight, overweight, and obesity.
How is BMI calculated?
In metric units, BMI equals your weight in kilograms divided by your height in meters squared (BMI = kg / m^2). In US or imperial units, BMI equals 703 times your weight in pounds divided by your height in inches squared (BMI = 703 x lb / in^2).
What is a healthy BMI for an adult?
Under standard World Health Organization (WHO) and CDC guidelines, a healthy adult BMI is between 18.5 and 24.9. For Asian and Indian populations, health guidelines often define a healthy BMI as 18.5 to 22.9.
Does BMI depend on age or sex for adults?
The adult BMI formula is the same for men and women aged 20 and older. However, women naturally tend to have more body fat than men at the same BMI, and older adults tend to have more body fat than younger adults.
Can I use this calculator for children or teenagers?
No. This calculator uses fixed adult cutoffs for ages 20 and up. Children and teens are still growing, so their BMI must be compared against age- and sex-specific growth percentiles from a doctor.
Why is there an Asian and Indian BMI option?
Research shows that people of South Asian and East Asian descent often face higher risks of type 2 diabetes and heart disease at lower BMI levels. Because of this, Asian guidelines set the overweight cutoff at 23.0 instead of 25.0.
What are the limitations of BMI?
BMI measures total weight against height, not body fat directly. Muscular athletes may have a high BMI even with low body fat, while older adults with low muscle mass may have a normal BMI despite carrying extra fat.
What are BMI Prime and Ponderal Index?
BMI Prime is the ratio of your BMI to the upper limit of a healthy BMI (25.0 in standard guidelines). A number below 1.00 means you are below the overweight threshold. Ponderal Index compares weight to height cubed (kg/m^3), which gives a fairer reading for very tall or very short people.
Are my height and weight stored or shared?
No. Every calculation runs directly inside your browser. Your measurements are never uploaded, saved, or shared.