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1. Print "Hello, World!"2. Add Two Numbers3. Swap Two Variables4. Find ASCII Value of a Character5. Check Even or Odd6. Find Largest of Two Numbers7. Find Largest of Three Numbers8. Check Positive, Negative, or Zero9. Convert Kilometers to Miles10. Convert Celsius to Fahrenheit11. Calculate Area of a Triangle12. Calculate Simple Interest13. Calculate Compound Interest14. Calculate Square Root15. Convert Seconds to Hours, Minutes, and Seconds16. Calculate Body Mass Index (BMI)17. Check Leap Year18. Find Absolute Value19. Calculate Age from Birth Year20. Sum of First N Natural Numbers21. Calculate Power Without Using pow()22. Print Multiplication Table23. Convert Decimal to Binary24. Convert Binary to Decimal25. Calculate Electricity Bill

Calculate Body Mass Index (BMI) in Python

weight / height². Height in metres. 175 cm is 1.75, not 175 — that BMI looks fatal.

BeginnerBasic Python ProgramsExample 16 of 25
calculate-body-mass-index-bmi.py
1# Program to calculate Body Mass Index (BMI)
2

3weight = float(input("Enter your weight in kg: "))
4height = float(input("Enter your height in meters: "))
5

6if height <= 0:
7    print("Height must be greater than zero.")
8else:
9    bmi = weight / (height ** 2)
10    print("Your BMI is:", round(bmi, 2))
11

12    if bmi < 18.5:
13        print("Category: Underweight")
14    elif bmi < 25:
15        print("Category: Normal weight")
16    elif bmi < 30:
17        print("Category: Overweight")
18    else:
19        print("Category: Obesity")

Output

Enter your weight in kg: 68
Enter your height in meters: 1.75
Your BMI is: 22.2
Category: Normal weight

In this one

  • height is metres. 175 cm → 1.75
  • height ** 2, not height * 2

What's going on

BMI = weight / height². Height in metres. Type 175 because you think in cm and the BMI is ~0.002. The categories will call you underweight, which is funny until it isn't.

height ** 2 is height squared. height * 2 is not.

The cutoffs (18.5, 25, 30) are the WHO buckets. They are blunt. The code doesn't know your sport or your bones.

height <= 0 is required. Divide by zero is a crash, not a category.

After this program

If the idea is still fuzzy, read Day 1: Introduction to Python in the Python course. For a short check, try the Python quiz (300 questions). Stay with all 25 basic python programs, or see every topic on Python exercises.

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