Converting division of int to int to a decimal is giving 0

Question

I came up with a formula to keep numbers a simple int and was surprised to see that the following was producing a 0.

var x = 45;
var y = 100;
var z = Convert.ToDecimal(x / y * 100);

In the above example, it almost seems ridicilous that I'm dividing by 100, then multiplying by 100 but in most cases, the x and y values are not nice integers.

When my x and y values end up being integers, the above conversion produces a 0. Why is that?

Because when you divide an integer with another integer the decimal result is not considered. 45 / 100 = 0 — Steve, Apr 21 '18 at 17:23
Just cast one of your integers to decimal ((decimal)x / y) * 100 — Steve, Apr 21 '18 at 17:25

score 2 · Accepted Answer · answered Apr 21 '18 at 17:23

2

X / Y = 0.45

Int conversion of 0.45 is 0.

Therefore 0 * 100 = 0.

Therefore Convert.ToDecimal(0) is 0.

answered Apr 21 '18 at 17:23

Erez Shlomo

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So, I need to `Convert.ToDecimal(x/y)` first, then continue with the rest of the computation? – Sam Apr 21 '18 at 17:24
Try converting to decimal one of them first, or define them as decimal from the beginning, if it's possible. – Erez Shlomo Apr 21 '18 at 17:25
2

@Sam You can simply do `x / (Decimal)y * 100`. – ProgrammingLlama Apr 21 '18 at 17:25
Got it! Thank you! – Sam Apr 21 '18 at 17:26

score 1 · Answer 2 · answered Apr 21 '18 at 17:25

This does look a bit odd, but the problem there is with the order the expressions are evaluated: first the arguments of Convert are evaluated, and that is done inintegers. That’s why the result is truncated.

You should replace the conversation with an expression that forces evaluation in decimals:

var z = 100M * x / z;

Converting division of int to int to a decimal is giving 0

2 Answers2