BMI Calculator
Calculate your Body Mass Index from height and weight.
Enter your measurements
For adults aged 20 and older using standard adult BMI categories.
Your BMI result
Enter your height and weight, then calculate your body mass index.
Your body mass index
24.2
Healthy weightWhat Is Body Mass Index (BMI)?
Body Mass Index, commonly called BMI, is a measurement that compares a person’s weight with their height. A BMI calculator provides a quick estimate used to classify adult weight ranges.
This free online BMI calculator supports both metric measurements in kilograms and centimetres and US customary measurements in pounds, feet and inches. You can calculate your BMI and compare the result with standard adult BMI categories.
BMI is a screening measure rather than a direct measurement of body fat. It should be considered alongside other information about your health, body composition and medical history.
How to Calculate BMI
You can calculate your Body Mass Index using either the metric or US customary formula.
Metric BMI formula: weight in kilograms divided by height in metres squared.
US BMI formula: 703 multiplied by weight in pounds, divided by height in inches squared.
Example: If you weigh 70 kg and are 170 cm tall, your BMI is 70 ÷ (1.70 × 1.70), or approximately 24.2.
Enter your measurements above to calculate your BMI automatically without doing the formula by hand.
Adult BMI Categories
For adults aged 20 and older, standard BMI categories are used to interpret the calculated number. After you calculate your BMI, the matching category below will be highlighted.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5–24.9 |
| Overweight | 25.0–29.9 |
| Obesity, class 1 | 30.0–34.9 |
| Obesity, class 2 | 35.0–39.9 |
| Obesity, class 3 | 40.0 or above |
What Is a Healthy BMI Range?
For adults, a BMI from 18.5 to below 25 is generally classified as the healthy-weight range. A BMI below 18.5 is classified as underweight, while a BMI of 25 or above falls into higher weight categories.
The calculator estimates a corresponding weight range for your height based on a BMI of 18.5–24.9. This is a general reference, not a personalised weight goal.
Age, muscle mass, body composition, fat distribution and other health factors can affect how BMI should be interpreted.
BMI Chart by Height and Weight
This BMI chart provides examples of how height and weight relate to BMI for adults. Values are approximate and are intended as a reference; use the calculator above for your own measurements.
| Height | Weight | Approximate BMI | Category |
|---|---|---|---|
| 5 ft 4 in | 120 lb | 20.6 | Healthy weight |
| 5 ft 6 in | 140 lb | 22.6 | Healthy weight |
| 5 ft 9 in | 160 lb | 23.6 | Healthy weight |
| 6 ft 0 in | 180 lb | 24.4 | Healthy weight |
| 6 ft 2 in | 200 lb | 25.7 | Overweight |
Understanding Your BMI Result
BMI vs Body Fat Percentage
BMI estimates weight relative to height, whereas body fat percentage estimates the proportion of body weight that consists of fat. These measurements provide different information about body composition.
A person with substantial muscle mass may have a higher BMI without having excess body fat. BMI also does not show where fat is distributed in the body.
For this reason, BMI should not be used alone to determine an individual’s health status.
Who Should Use an Adult BMI Calculator?
This calculator is designed for adults aged 20 and older who want a quick estimate of Body Mass Index using pounds and inches or kilograms and centimetres.
- Adults checking their BMI category.
- People comparing metric and US customary measurements.
- Anyone looking for a general healthy-weight reference.
- Users who want to understand the standard adult BMI ranges.
Children and teenagers need a different assessment based on age and sex. Pregnant people should seek appropriate guidance rather than relying on this adult BMI tool.
BMI Calculator FAQs
What is a BMI calculator?
A BMI calculator estimates Body Mass Index using height and weight. It provides a screening measure commonly used to classify adult weight categories, but it does not directly measure body fat or diagnose a health condition.
How do I calculate BMI using kg and cm?
Convert height from centimetres to metres, square the height, and divide weight in kilograms by that number. For example, 70 kg divided by (1.70 × 1.70) gives a BMI of approximately 24.2.
How do I calculate BMI using pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. You can select US units in this calculator and enter your height in feet and inches and your weight in pounds.
What is a normal BMI for adults?
For adults aged 20 and older, a BMI from 18.5 to below 25 is generally classified as healthy weight. BMI is a screening measure and should be interpreted alongside other health information.
Is BMI different for men and women?
The standard adult BMI formula and categories are the same for men and women. However, BMI does not account for individual differences in muscle mass, body composition or fat distribution.
Can muscular people have a high BMI?
Yes. BMI cannot distinguish muscle from fat, so some people with high muscle mass may have a higher BMI. Other measures and professional assessment may be useful when interpreting the result.
Can I use this BMI calculator for children?
No. This calculator uses standard adult BMI categories. Children and teenagers require BMI-for-age assessments that account for age and sex.
Does a healthy BMI guarantee good health?
No. BMI is only one screening measure. It does not directly assess blood pressure, cholesterol, fitness, body fat distribution or every factor that affects health.
What is the difference between BMI and ideal body weight?
BMI relates weight to height and places the result into a category. Ideal body weight estimates use different formulas and assumptions. Neither measurement alone determines the most appropriate weight for an individual.
How accurate is an online BMI calculator?
A BMI calculator can accurately calculate the ratio of height and weight when the measurements are entered correctly. However, the BMI value itself does not fully describe body composition or individual health.