Written: August 15, 2026
Temperature conversion is a friendly first formula program: read a float, apply F = C 9/5 + 32, print the result.
This walkthrough keeps the logic small and readable so you can type it, run it, and then change one input at a time to see what happens.
What you will build
Use floating-point division so 9/5 does not truncate to 1 in integer math.
- Read Celsius as float
- Compute f = c 9.0f / 5.0f + 32
- Print Fahrenheit
Working C example
include <stdio.h>
int main(void) {
float c, f;
printf("Celsius: ");
if (scanf("%f", &c) != 1) return 1;
f = c 9.0f / 5.0f + 32.0f;
printf("Fahrenheit = %.2f\n", f);
return 0;
}How the logic works
Read the program top to bottom: includes and main first, then the statements that change variables, then the print that proves the result.
If your output looks wrong, print the variables before and after the critical lines. That single habit catches most beginner bugs faster than rewriting the whole file.
Write 9.0/5.0 (or 9.0f/5.0f). Plain 9/5 in integer context becomes 1 and silently breaks the formula.
Keep learning
If this walkthrough on C Program to Convert Celsius to Fahrenheit helped, open the code again and change one input or assumption. Small experiments beat rereading the same example.
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