C# how to always round down to nearest 50

Question

I've done a search on C# rounding, but haven't been able to find the answer to my current problem.

What I want to do is always round down to the nearest 50. All the values I want to round down will be in decimal.

So 635.25 would be 600.

298.42 would be 250.

149.56 would be 100.

I've looked at math.round but how would I use that so it always rounds down to the nearest 50 and never up?

This is a very popular question. One example: http://stackoverflow.com/questions/2826262/round-a-decimal-to-the-nearest-quarter-in-c-sharp — Jason Evans, Feb 22 '13 at 15:59
@AdrianCarneiro: Given programming languages handle this differently (maybe not with this example, but in the presence of a negative number), I would have to disagree. — leppie, Feb 22 '13 at 16:07
I kept finding ones that would round up and down and not just down, missed that, thanks — saintsfanuk, Feb 22 '13 at 16:10
@leppie Agreed.This is why I said it is "more of a math question", not "definitely a math question" — Adriano Carneiro, Feb 22 '13 at 16:28

score 47 · Accepted Answer · answered Feb 22 '13 at 16:00

47

Divide the value by 50, round down to the closest whole number, and multiply by 50 again:

double n = Math.Floor(n / 50.0) * 50.0;

answered Feb 22 '13 at 16:00

Guffa

Did not notice the never round up +1 :) – leppie Feb 22 '13 at 16:01
Oh well, added an alternative ;) Might be cheaper if you are into micro optimizations ;p – leppie Feb 22 '13 at 16:03

score 5 · Answer 2 · answered Feb 22 '13 at 16:00

5

Another way to Guffa's:

(((int) value) / 50) * 50

answered Feb 22 '13 at 16:00

leppie

This is not the same as Guffa's answer. Negative numbers are rounded up here. – Jens Oct 08 '13 at 09:03
@Jens: Given positive numbers, it is the same :) – leppie Oct 08 '13 at 12:17

score 4 · Answer 3 · answered Mar 19 '18 at 15:53

4

Using modulus:

var roundedDownToClosestFifty = value - (value % 50);

answered Mar 19 '18 at 15:53

Repo

3 Answers3