#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    float fahrenheit, celsius;
    
    cout << "Enter temperature in Fahrenheit: ";
    cin >> fahrenheit;
    
    // Formula: C = (F - 32) * 5/9
    celsius = (fahrenheit - 32) * 5.0 / 9.0;
    
    cout << fixed << setprecision(2);
    cout << fahrenheit << "°F = " << celsius << "°C" << endl;
    
    return 0;
}

Enter temperature in Fahrenheit: 98.6
98.60°F = 37.00°C

Convert Fahrenheit to Celsius in C++

This program helps you convert a temperature from Fahrenheit to Celsius. It uses a well-known formula from science and applies it using simple arithmetic in C++. The program also shows how to format decimal numbers so they look neat and easy to read.

1. Why Convert Fahrenheit to Celsius?

Temperature is measured differently in different places:

• The United States mostly uses Fahrenheit (°F)
• Most other countries use Celsius (°C)

This program teaches how to convert between the two using math.

2. Header Files

The program uses two headers:

1. #include <iostream>
   Allows us to use cin (input) and cout (output).

2. #include <iomanip>
   Provides tools like fixed and setprecision() to control how decimal numbers are printed.

3. Declaring Float Variables

We use:

float fahrenheit, celsius;

• fahrenheit → stores the temperature entered by the user
• celsius → stores the converted temperature

We use float because temperature often includes decimal values (e.g., 98.6°F).

4. Taking Input From the User

The program displays:

cout << "Enter temperature in Fahrenheit: ";
cin >> fahrenheit;

Whatever the user types (like 98.6) is stored in the variable fahrenheit.

5. The Conversion Formula

The conversion formula is:

C = (F - 32) × 5/9

This formula converts a temperature from the Fahrenheit scale to the Celsius scale.

In the program:

celsius = (fahrenheit - 32) * 5.0 / 9.0;

Here's why we use ## 5.0 / 9.0 instead of 5 / 9:

• 5 / 9 (without decimal) would perform integer division → result = 0
• 5.0 / 9.0 performs floating-point division → correct result ≈ 0.5555

So 5.0 and 9.0 ensure accurate decimal calculations.

6. Formatting the Decimal Output

Before printing the final result, the program uses:

cout << fixed << setprecision(2);

This means:

• fixed → show numbers in normal decimal form
• setprecision(2) → show exactly 2 decimal places

So:

• 98.6 becomes 98.60
• 37 becomes 37.00

This makes the output clean and professional.

7. Displaying the Result

The output is printed as:

cout << fahrenheit << "°F = " << celsius << "°C" << endl;

If the user enters 98.6, the program prints:

98.60°F = 37.00°C

Summary

• The program reads a temperature in Fahrenheit.
• It converts it to Celsius using the formula C = (F - 32) × 5/9.
• Floating-point numbers ensure accurate calculations.
• setprecision(2) formats the output to two decimal places.
• This is a simple and practical program used in many real-world applications.

This example helps build confidence with arithmetic, formulas, and formatted output in C++.