C program to convert Fahrenheit to Celsius always prints zero

5/9 will result in integer division, which will = 0

Try 5.0/9.0 instead.

You problem is here :

celsius = (5/9) * (fahrenheit-32);

5/9 will always give you 0. Use (5.0/9.0) instead.

try celsius = ((double)5/9) * (fahrenheit-32); Or you can use 5.0.

The fact is that "/" looks at the operand type. In case of int the result is also an int, so you have 0. When 5 is treated as double, then the division will be executed correctly.