BMI Calculator

Q: What is a good BMI number?

A good BMI is between 18.5 and 24.9 . This range is called "Healthy Weight." It means your weight fits well with your height. Numbers below 18.5 mean underweight, 25 to 29.9 means overweight, and 30 or above means obese.

BMI Calculator

Updated May 27, 2026 By Jehan Wadia

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. You must be between 2 and 120 years old. If you need to find your exact age, our Age Calculator can help.

Gender: Select Male or Female. This is saved for your reference.

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. If you need to convert between meters and feet, try our Meters to Feet Calculator. You can also explore our Height Calculator to estimate future height.

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 or check your Lean Body Weight.

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. You do not need to do the math yourself — the calculator above does it for you instantly.

What Do the BMI Categories Mean?

Underweight (below 18.5): Your weight may be too low. Talk to a doctor about healthy ways to gain weight. Our Weight Gain Calculator can help you set a safe plan, and the Calorie Calculator can show you how many calories you need each day.
Healthy Weight (18.5 to 24.9): Your weight is in a good range for your height. To maintain it, tools like the Macro Calculator and Water Intake Calculator can support your daily habits.
Overweight (25.0 to 29.9): You may carry extra weight. Small changes in diet and exercise can help. Our Weight Loss Calculator can help you set realistic goals, and the Calories Burned Calculator can show the impact of physical activity.
Obese (30.0 and above): Your weight may put your health at higher risk. A doctor can help you make a safe plan. You can also use the TDEE Calculator to understand your total daily energy expenditure.

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. For a fuller picture, consider checking your Waist to Hip Ratio, Waist to Height Ratio, or using the Ideal Body Weight Calculator. Athletes may find the FFMI Calculator more useful since it accounts for muscle mass. You can also explore your BMR (Basal Metabolic Rate) and BSA (Body Surface Area) for additional body metrics. Children and teens are measured on special growth charts, not the standard adult scale — our Baby Percentile Calculator can help track growth in younger children. Always talk to a healthcare provider for a full picture of your health.

Frequently asked questions

What is a good BMI number?

A good BMI is between 18.5 and 24.9. This range is called "Healthy Weight." It means your weight fits well with your height. Numbers below 18.5 mean underweight, 25 to 29.9 means overweight, and 30 or above means obese.

Does BMI work the same for men and women?

The BMI formula is the same for men and women. However, women usually carry more body fat than men at the same BMI number. That is why BMI is a screening tool, not a final answer. A doctor can give you a fuller picture based on your gender and body type.

Is BMI accurate for kids and teenagers?

BMI works differently for kids and teens. For people under 20, BMI is compared to growth charts based on age and gender. A child's BMI is shown as a percentile rather than a fixed category. This calculator accepts ages 2 and up, but children should always be evaluated by a pediatrician.

Why does the calculator ask for my age and gender?

Age and gender help give context to your results. Body fat levels change as you get older, and men and women store fat differently. While the BMI formula itself stays the same, knowing your age and gender helps you and your doctor interpret the number more accurately.

What does the Mixed unit option do?

The Mixed option lets you use different units for height and weight. For example, you can enter your height in centimeters but your weight in pounds. This is helpful if you know your measurements in different systems and do not want to convert them first.

Can I use this BMI calculator if I am very tall or very short?

Yes, but BMI may be less accurate at extreme heights. For very tall people, BMI can overestimate body fat. For very short people, it can underestimate it. The Ponderal Index shown in your results handles height differences better and may be more useful in these cases.

What does the BMI scale bar show?

The colored bar shows the full BMI range from underweight to obese. Blue means underweight, green means healthy, orange means overweight, and red means obese. A black marker shows exactly where your BMI falls on the scale so you can see your result at a glance.

What does the Weight to Reach Healthy result mean?

This tells you how much weight you need to gain or lose to reach the healthy BMI range. If you are already in the healthy range, it will say "Already healthy!" If not, it shows the exact amount in pounds or kilograms depending on your chosen unit.

How often should I check my BMI?

Checking your BMI once every few months is enough for most people. Your weight can change day to day due to water, food, and activity. Tracking BMI over time gives a better picture than any single reading. Weigh yourself at the same time of day for the most consistent results.

Does a high BMI always mean I am unhealthy?

No. BMI does not separate muscle from fat. Athletes, bodybuilders, and people with large frames can have a high BMI while being very fit. BMI is a starting point, not a diagnosis. Talk to your doctor if your BMI is high but you exercise regularly and eat well.

What is the BMI vs Weight chart in the results?

This chart shows how your BMI changes as your weight goes up or down at your current height. It draws a smooth curve with dotted lines at BMI 18.5, 25, and 30 to mark category boundaries. A dot marks your current position so you can see how close you are to each range.

What does the reference table at the bottom show?

The reference table lists every BMI category from Severe Thinness to Obese Class III. For each category, it shows the BMI range and the matching weight range for your specific height. Your current category is highlighted with a green row and an arrow so it is easy to find.

Can BMI predict health problems?

A BMI outside the healthy range is linked to higher risk for heart disease, type 2 diabetes, high blood pressure, and certain cancers. However, BMI alone cannot predict these conditions. Other factors like diet, exercise, family history, and where your body stores fat also play a big role.

Why is my BMI different from what my doctor told me?

Small differences can come from when you weigh yourself, what you are wearing, or the scale used. Make sure you enter your exact height and weight. Doctors may also round differently or use adjusted scales for certain populations. If the difference is large, double-check your input values.