Rounding in C#. Net

Question

I have an MVC3 C#.Net web app. The product of a calculation is 158 * 1.75 = 276.5. I want this number to round up to 277. I am using Math.Round but it rounds down. I know I've seen this issue before somewhere. What's the solution?

Refer to this question: http://stackoverflow.com/questions/977796/in-c-math-round2-5-result-is-2-instead-of-3-are-you-kidding-me — Andrei Dvoynos, Sep 19 '12 at 21:35

score 6 · Accepted Answer · answered Sep 19 '12 at 21:34

6

Use the overload that takes a MidpointRounding

Math.Round(276.5, MidpointRounding.AwayFromZero);

demo: http://ideone.com/sQ26z

answered Sep 19 '12 at 21:34

Tim Schmelter

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It is interesting to note that if you use a format string to convert the number to a string representation with zero decimals, that is `string output = (276.5).ToString("F0");`, then the away-from-zero rule is also used. I don't think that the to-even rule is ever used when string formatting a number. – Jeppe Stig Nielsen Sep 19 '12 at 21:47
@All...that's great. Thanks for the feedback – MikeTWebb Sep 19 '12 at 21:59

score 4 · Answer 2 · answered Sep 19 '12 at 21:37

4

As already mentioned, you can use Math.Round(d, MidpointRounding.AwayFromZero).

By default, .NET uses the so called bankers rounding (or MidpointRounding.ToEven)

answered Sep 19 '12 at 21:37

Zdeslav Vojkovic

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score 2 · Answer 3 · answered Sep 19 '12 at 21:36

.NET uses bankers' rounding by default; it rounds values ending in 5 to the nearest even significant digit, and not always up (called "semantic arithmetic rounding"). The reason is that if you round a bunch of random decimal numbers and then sum them, when using banker's rounding that sum will be closer to the sum of the unrounded numbers than the sum of arithmetically-rounded numbers would be.

To force it to use grade-school rounding rules, use the overload accepting a MidpointROunding enum value:

Math.Round(myNumber, MidpointRounding.AwayFromZero);

score 0 · Answer 4 · answered Sep 19 '12 at 21:35

0

Use:

Math.Round(value, MidpointRounding.AwayFromZero);

answered Sep 19 '12 at 21:35

NominSim

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score -1 · Answer 5 · answered Sep 19 '12 at 21:34

-1

Try using Math.Ceiling instead

answered Sep 19 '12 at 21:34

Johnny

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The OP (I am assuming) likely wants 276.1 to round to 276, not 277. – NominSim Sep 19 '12 at 21:36
@NominSim...that is true 276.1 should be 276 and 276.5 should be 277 – MikeTWebb Sep 19 '12 at 21:56

Rounding in C#. Net

5 Answers5