Temperature Converter in C++

Last Updated : 19 Jul, 2025

In this project, you will build a simple command-line application that allows users to convert temperatures between Celsius and Fahrenheit. The program should take the user’s choice, perform the appropriate conversion, and display the result. It should continue running based on the user's input and handle invalid choices appropriately, as described in the features below.

Features

Our temperature converter program will have the following features:

Convert Celsius to Fahrenheit
Convert Fahrenheit to Celsius
Validate user input for menu selection
Keep running until the user chooses to exit

Example:

C++

Temperature Converter 1. Celsius to Fahrenheit 2. Fahrenheit to Celsius 3. Exit Enter your choice (1-3): 1 Enter temperature in Celsius: 25 25 C = 77 F Temperature Converter 1. Celsius to Fahrenheit 2. Fahrenheit to Celsius 3. Exit Enter your choice (1-3): 2 Enter temperature in Fahrenheit: 98.6 98.6 F = 37 C Temperature Converter 1. Celsius to Fahrenheit 2. Fahrenheit to Celsius 3. Exit Enter your choice (1-3): 4 Invalid choice. Please try again. Temperature Converter 1. Celsius to Fahrenheit 2. Fahrenheit to Celsius 3. Exit Enter your choice (1-3): 3 Exiting temperature converter.

Try to solve this yourself before looking at the solution below.

Project Requirements

You must be familiar with the following topics in C++:

Variable, Data Types and Constants
Basic input/output
Operators
Decision Making and Loops

Implementation

We start by defining constexpr constants for the conversion factors.

Then, we use a while (true) loop to keep the converter running. Inside the loop, we display a menu and take user input. Based on the input, the appropriate conversion is performed. Input is validated to handle invalid menu choices.

C++

#include <iostream> using namespace std; // Define conversion constants const double celToFahMult = 9.0 / 5.0; const double fahToCelMult = 5.0 / 9.0; const int fahOffset = 32; int main() {  int choice;  double temp, converted;  // Repeat until user chooses to exit  while (true) {  // Display menu  cout << "\nTemperature Converter\n";  cout << "1. Celsius to Fahrenheit\n";  cout << "2. Fahrenheit to Celsius\n";  cout << "3. Exit\n";  cout << "Enter your choice (1-3): ";  cin >> choice;  // Exit condition  if (choice == 3) {  cout << "Exiting temperature converter.\n";  break;  }  // Celsius to Fahrenheit  if (choice == 1) {  cout << "Enter temperature in Celsius: ";  cin >> temp;  converted = (temp * celToFahMult) + fahOffset;  cout << temp << " C = " << converted << " F\n";  }  // Fahrenheit to Celsius  else if (choice == 2) {  cout << "Enter temperature in Fahrenheit: ";  cin >> temp;  converted = (temp - fahOffset) * fahToCelMult;  cout << temp << " F = " << converted << " C\n";  }  // Invalid choice  else {  cout << "Invalid choice. Please try again.\n";  }  }  return 0; }