Your weight alone does not always tell you much about your body size.
BMI Calculator
Calculate your Body Mass Index (BMI) using your height and weight, and view the standard adult BMI category associated with the result.
BMI History
Your last 10 calculations are stored only in this browser.
Calculate your BMI and your recent results will appear here.
Your data stays private. BMI history is stored locally in this browser and is not sent to SlimDownToday.
How BMI Is Calculated
This calculator is designed for adults age 18 and older.
You can use US units with pounds, feet and inches, or metric units with kilograms and centimeters.
BMI compares body weight with height using a standard mathematical formula.
Your result is displayed with the standard adult BMI category and a height-based reference weight range.
BMI Formula
Adult BMI Categories
A BMI Calculator uses your height and weight to calculate a number called Body Mass Index, or BMI.
BMI is a simple measurement commonly used to compare body weight with height.
Our BMI Calculator makes the calculation quick and easy.
Enter your height and weight to get your estimated BMI in seconds.
What Is BMI?
BMI stands for Body Mass Index.
It is a number calculated using your height and weight.
BMI does not directly measure body fat. Instead, it provides a simple way to compare weight with height.
For adults, BMI is commonly grouped into general categories.
These categories can help provide basic information about body size, but BMI should not be used alone to judge a person’s health.
What Is a BMI Calculator?
A BMI Calculator is an online tool that calculates your Body Mass Index automatically.
Instead of doing the math yourself, you simply enter your:
- Height
- Weight
Then click Calculate.
The calculator will show your BMI.
Depending on the tool, it may also display the general BMI category associated with the result.
How Is BMI Calculated?
The BMI formula depends on the measurement system you use.
BMI Formula Using Kilograms and Meters
If your weight is measured in kilograms and your height is measured in meters, the formula is:
BMI = Weight (kg) ÷ Height² (m²)
For example:
Weight: 70 kg
Height: 1.75 m
First, calculate height squared:
1.75 × 1.75 = 3.0625
Then:
70 ÷ 3.0625 = 22.86
The BMI is approximately:
22.9
BMI Formula Using Pounds and Inches
If you use pounds and inches, the formula is:
BMI = Weight (lb) ÷ Height² (in²) × 703
For example:
Weight: 160 lb
Height: 70 inches
Calculation:
160 ÷ (70 × 70) × 703
The BMI is approximately:
23.0
Our BMI Calculator performs these calculations automatically.
How to Use the BMI Calculator
Using our BMI Calculator is simple.
Step 1: Select Your Units
Choose your preferred measurement system.
You may be able to use:
Metric: kilograms and centimeters
or
US/Imperial: pounds and feet/inches
Step 2: Enter Your Height
Enter your current height.
Make sure you select the correct unit.
Step 3: Enter Your Weight
Enter your current body weight.
Step 4: Calculate Your BMI
Click Calculate.
The calculator will display your estimated BMI and may also show the general category associated with your result.
Adult BMI Categories
For adults, commonly used BMI categories are:
| BMI | General Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy Weight |
| 25.0 – 29.9 | Overweight |
| 30.0 or higher | Obesity |
These categories are general screening categories.
BMI is not a diagnosis.
A healthcare professional may consider many other factors when evaluating a person’s health.
BMI Example
Imagine a person who weighs 80 kilograms and is 1.80 meters tall.
The formula is:
BMI = 80 ÷ (1.80 × 1.80)
First:
1.80 × 1.80 = 3.24
Then:
80 ÷ 3.24 = 24.69
The estimated BMI is:
24.7
The calculator can perform this calculation instantly.
Why Is BMI Used?
BMI is popular because it is simple.
It only requires two basic measurements:
Height + Weight
No special equipment is needed.
Because of this, BMI is often used as a general screening measurement.
However, BMI does not provide a complete picture of a person’s body composition or health.
Is BMI the Same as Body Fat Percentage?
No.
BMI and body fat percentage are different measurements.
BMI compares your weight with your height.
Body fat percentage estimates how much of your body weight comes from fat.
For example, two people may have:
- The same height
- The same weight
- The same BMI
But one person may have more muscle and less body fat.
The other person may have less muscle and more body fat.
Their BMI can be identical even though their body composition is different.
Does BMI Measure Body Fat?
No.
BMI does not directly measure body fat.
The calculation only uses height and weight.
It does not directly measure:
- Body fat
- Muscle mass
- Bone mass
- Body water
- Fat distribution
This is one of the main limitations of BMI.
If you want an estimate of body fat, a Body Fat Calculator may provide additional information.
BMI and Muscle
People with a large amount of muscle can sometimes have a higher BMI.
For example, an athlete may weigh more because of muscle mass.
Since BMI does not know whether body weight comes from muscle, fat, water, or other tissues, the number may not fully represent that person’s body composition.
This is why BMI should be interpreted with context.
BMI and Age
BMI is interpreted differently for children and teenagers than for adults.
For adults, fixed BMI ranges are commonly used.
For children and teens, BMI is generally interpreted using age- and sex-specific growth references.
For this reason, an adult BMI Calculator should not automatically be used to evaluate a child.
BMI for Men and Women
The BMI formula for adults uses height and weight.
The basic calculation is the same for adult men and women.
However, people with the same BMI can have different body compositions.
Sex, age, genetics, muscle mass, and other factors can influence body fat and body composition.
BMI alone cannot measure these differences.
What Can Affect Your BMI?
BMI changes when your weight or height changes.
For most adults, height stays relatively stable, so changes in BMI usually happen because of changes in body weight.
For example:
If your weight increases, your BMI usually increases.
If your weight decreases, your BMI usually decreases.
However, BMI cannot tell whether that weight change came from:
- Fat
- Muscle
- Water
- Other body tissues
This is why additional measurements may sometimes be useful.
BMI and Weight Loss
If you are trying to lose weight, your BMI may decrease as your body weight decreases.
For example:
Starting BMI: 30
After losing weight:
New BMI: 27
This shows that your weight relative to your height has changed.
However, BMI does not tell you exactly how much body fat you lost.
You may want to use BMI together with other measurements to track progress.
BMI and Weight Gain
BMI can also change when you gain weight.
This can happen because of increased:
- Body fat
- Muscle
- Water
- Other body mass
The BMI calculation cannot tell the difference.
If your goal is to gain muscle, body weight and BMI may not provide enough information by themselves.
BMI vs. Ideal Weight
BMI and ideal weight calculators answer different questions.
A BMI Calculator tells you your Body Mass Index based on your current height and weight.
An Ideal Weight Calculator estimates a weight range or reference weight using specific formulas.
Neither tool can determine the perfect weight for every individual.
Your health, body composition, age, lifestyle, and other factors can also matter.
BMI vs. Body Fat Calculator
These tools can be used for different purposes.
A BMI Calculator uses:
Height + Weight
A Body Fat Calculator may use:
Height + Waist + Neck + Hips + Other Information
Because they use different information, the results describe different aspects of your body.
BMI is simple and fast.
Body fat calculations may provide additional information about estimated body composition.
BMI vs. Waist Measurement
Waist circumference is another measurement sometimes used when looking at body size and health risk.
BMI looks at weight relative to height.
Waist circumference focuses on the size around the waist.
These measurements provide different information.
A healthcare professional may consider both measurements along with other health information.
Is BMI Accurate?
The BMI calculation itself is mathematically simple.
If your height and weight are correct, your BMI calculation can be calculated accurately.
The bigger question is what that number means for an individual person.
BMI does not directly measure body composition.
It cannot distinguish between muscle and fat.
It also does not provide information about where body fat is located.
For these reasons, BMI is best viewed as a general screening tool rather than a complete health assessment.
Is BMI a Diagnosis?
No.
BMI is not a medical diagnosis.
A BMI result alone cannot determine whether someone is healthy or unhealthy.
Health can depend on many factors, including:
- Blood pressure
- Blood glucose
- Cholesterol
- Physical activity
- Nutrition
- Sleep
- Medical history
- Body composition
- Genetics
- Lifestyle
A healthcare professional can consider these factors together when evaluating health.
How to Track Your BMI
If you are tracking changes in body weight, you can calculate your BMI periodically.
For example, you could record:
Date → Weight → BMI
This can make it easier to see changes over time.
Remember that body weight naturally changes from day to day.
Water, food, exercise, and other factors can cause temporary changes.
Looking at longer-term trends may be more useful than focusing on a single measurement.
Table of Contents
Frequently Asked Questions
What does BMI mean?
BMI stands for Body Mass Index. It is a number calculated using your height and weight.
How do I calculate my BMI?
For metric measurements, divide your weight in kilograms by your height in meters squared.
BMI = kg ÷ m²
You can also use our BMI Calculator to calculate it automatically.
What information do I need for a BMI Calculator?
You normally only need your height and weight.
Does BMI measure body fat?
No. BMI does not directly measure body fat. It only compares body weight with height.
Is BMI the same as body fat percentage?
No. BMI uses height and weight, while body fat percentage estimates the proportion of your body weight that comes from fat.
Can a muscular person have a high BMI?
Yes. BMI does not distinguish between muscle and fat, so people with more muscle can sometimes have a higher BMI.
Is BMI different for men and women?
The standard adult BMI calculation uses the same formula. However, body composition can differ between individuals even when BMI is the same.
Can children use an adult BMI Calculator?
BMI for children and teenagers is generally interpreted using age- and sex-specific growth references. An adult BMI Calculator should not automatically be used to evaluate children.
Can BMI tell me my ideal weight?
BMI can show how your weight compares with your height, but it does not determine a perfect weight for every person.
Can BMI change when I build muscle?
Yes. If your body weight increases because you gain muscle, your BMI can also increase.
How often should I calculate my BMI?
There is usually no need to calculate it every day. If you are tracking weight changes, you can calculate it periodically and focus on longer-term trends.
Is BMI Calculator accurate?
The mathematical calculation is straightforward when height and weight are entered correctly. However, BMI has limitations because it does not directly measure body fat or body composition.
Does BMI tell me if I am healthy?
No single BMI number can determine your overall health. BMI is a screening measurement and should be considered together with other health information.
Calculate Your BMI
Knowing your BMI can give you a simple way to compare your body weight with your height.
Our BMI Calculator makes the calculation easy.
Simply enter your:
Height + Weight
Then click Calculate to see your Body Mass Index.
You can use the result as general information and track changes over time.
Remember that BMI is only one measurement and does not provide a complete picture of your health or body composition.
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Disclaimer:
This BMI Calculator is provided for informational and educational purposes only. BMI is a general screening measurement and does not directly measure body fat, body composition, or overall health. Adult BMI categories should not automatically be applied to children or teenagers. The results are not a medical diagnosis and do not replace advice from a qualified healthcare professional.