# Simple Guide to write a BMI Calculator app in Python

What is BMI?

The Body Mass Index (BMI) is a measurement of a person's leanness or corpulence based on their height and weight and is intended to quantify tissue mass. It is widely used as a general indicator of whether a person has a healthy body weight for their height. Specifically, the value obtained from the calculation of BMI is used to categorize whether a person is underweight, normal weight, overweight, or obese depending on what range the value falls between.

Come on to build a simple BMI Calculator

## How does it work?

A BMI Calculator will take in the height and weight individually and will calculate the BMI of the user.

Body mass index (BMI) is a measure of body fat based on height and weight.

Based on the BMI of the individual, it will print a statement stating the overall health case of the user.

Coding Time :)

The first thing we need to do is to ask the user about their height & weight.

```
height = float(input("Enter your height in cm: "))
weight = float(input("Enter your weight in kg: "))
```

We used float() to convert the input string to float so that we can perform calculations with it.

Next, we have to calculate the BMI.

The formula to calculate BMI is:

So, the implementation of this formula in python will be:

`BMI = weight / (height/100)**2`

Here we will be dividing the height by 100 to convert the centimeters into meters.

to print BMI:

`print(f"Your BMI is {BMI}")`

Now we have to print a statement to state the current health case of the user based on their BMI.

And to implement this classification we use a simple if-else condition:

```
if BMI <= 18.4:
print("You are underweight !")
elif BMI <= 24.9:
print("You are healthy :)")
elif BMI <= 29.9:
print("You are over weight !")
elif BMI <= 34.9:
print("You have obesity class 1 !")
elif BMI <= 39.9:
print("You have obesity class 2 !")
else:
print("You have obesity class 3 !")
```

The output will be:

if BMI is less than or equal to 18.4 then You are underweight ! will be printed.

if BMI is less than or equal to 24.9 then You are healthy :) will be printed.

if BMI is less than or equal to 29.9 then You are over weight ! will be printed.

if BMI is less than or equal to 34.9 then You have obesity class 1 ! will be printed.

if BMI is less than or equal to 39.9 then You have obesity class 2 ! will be printed.

if BMI none of the above are true then You have obesity class 3 ! will be printed.

That's it, I hope this article was worth reading and helped you acquire new knowledge no matter how small.

Feel free to check up on the notebook. You can find the results of code samples in this post.