Introduction
A BMI calculator helps you find out if your weight is healthy for your height. BMI stands for Body Mass Index. It is a simple number that uses your height and weight to estimate how much body fat you have. Doctors and health experts use BMI as a quick screening tool to spot weight problems in adults and children.
This free BMI calculator lets you enter your height and weight in pounds, kilograms, feet, or centimeters. It gives you your BMI score, shows what category you fall in, and tells you the healthy weight range for your height. You also get a visual chart and a full reference table so you can see exactly where you stand.
How to Use Our BMI Calculator
Enter your age, gender, height, and weight below. The calculator will instantly show your BMI number, weight category, healthy weight range, and a visual chart.
Unit System: Pick how you want to measure. Choose US/Imperial for feet and pounds, Metric for centimeters and kilograms, or Mixed if you want to combine both.
Age: Type your age in years, from 2 to 120. For ages 2 to 19 a Months Since Birthday box appears: fill it in for a more exact reading, or leave it blank to use the middle of the year.
Gender: Select Male or Female. For ages 2 to 19 BMI is compared with other boys or girls of the same age, so the result depends on it. Adult categories are the same for men and women.4
Height: Enter how tall you are. In US mode, pick your feet and inches from the dropdowns. In Metric mode, type your height in centimeters. In Mixed mode, you can choose either option.
Weight: Enter how much you weigh. In US mode, type your weight in pounds. In Metric mode, type it in kilograms. In Mixed mode, pick pounds or kilograms.
Calculate: Click the Calculate button to see your results. Your BMI score, category, healthy weight range, and a weight-to-BMI chart will appear on the right side of the screen.
Reset: Click the Reset button to clear all fields and start over with the default values.
What Is BMI?
BMI stands for Body Mass Index. It is a simple number that tells you if your weight is healthy for your height. Doctors and health experts use BMI as a quick screening tool. It does not measure body fat directly, but it gives a good starting point to check if you might be underweight, at a healthy weight, overweight, or obese. For a more detailed look at body composition, you may also want to use a Body Fat Calculator.
How Is BMI Calculated?
BMI is found by dividing your weight in kilograms by your height in meters squared. The formula looks like this: BMI = weight (kg) ÷ height (m) × height (m). If you use pounds and inches, the formula multiplies by 703 to get the same result.1 You do not need to do the math yourself. The calculator above works it out instantly.
What Do the BMI Categories Mean?
- Underweight (below 18.5): Your weight may be too low.1 Talk to a doctor about healthy ways to gain weight.
- Healthy Weight (18.5 to 24.9): Your weight is in a good range for your height.1
- Overweight (25.0 to 29.9): You may carry extra weight.1 Small changes in diet and exercise can help.
- Obese (30.0 and above): Your weight may put your health at higher risk.1 A doctor can help you make a safe plan.
These ranges are for adults aged 20 and over.4 For ages 2 to 19 the calculator shows the BMI-for-age percentile and uses the CDC child and teen categories instead: underweight below the 5th percentile, healthy weight from the 5th to below the 85th, overweight from the 85th to below the 95th, obesity at the 95th or above, and severe obesity at 120% of the 95th percentile or a BMI of 35 or more.3 The Weight to Reach Healthy and BMI Prime figures are shown for adults only.
What Is BMI Prime?
BMI Prime is your BMI divided by 25. A BMI Prime of 1.0 means you are right at the upper edge of the healthy range. If your number is below 1.0, you are within or under the healthy range. If it is above 1.0, you are above the healthy range. It is a quick way to see how close or far you are from a healthy BMI.
What Is the Ponderal Index?
The Ponderal Index is similar to BMI but uses height cubed instead of height squared. This makes it work better for very tall or very short people. It gives a more even comparison across different heights.
Limitations of BMI
BMI does not tell the whole story. It cannot tell the difference between muscle and fat. A strong, muscular person may have a high BMI but still be very healthy. Age, gender, bone density, and where your body stores fat all matter too. Athletes may find the FFMI Calculator more useful since it accounts for muscle mass. Children and teens are measured on special growth charts, not the standard adult scale. Always talk to a healthcare provider for a full picture of your health.