How to round a integer to the close hundred?

Question

I don\'t know it my nomenclature is correct! Anyway, these are the integer I have, for example :

76
121
9660

And I\'d like to round them to

Answer 1

Just some addition to @krizzzn's accepted answer...

Do note that the following will return 0:

Math.Round(50d / 100d, 0) * 100;

Consider using the following and make it return 100 instead:

Math.Round(50d / 100d, 0, MidpointRounding.AwayFromZero) * 100;

Depending on what you're doing, using decimals might be a better choice (note the m):

Math.Round(50m / 100m, 0, MidpointRounding.AwayFromZero) * 100m;

Answer 2

Try the Math.Round method. Here's how:

Math.Round(76d / 100d, 0) * 100;
Math.Round(121d / 100d, 0) * 100;
Math.Round(9660d / 100d, 0) * 100;

Answer 3

I know this is an old thread. I wrote a new method. Hope this will be useful for some one.

    public static double Round(this float value, int precision)
    {
        if (precision < -4 && precision > 15)
            throw new ArgumentOutOfRangeException("precision", "Must be and integer between -4 and 15");

        if (precision >= 0) return Math.Round(value, precision);
        else
        {
            precision = (int)Math.Pow(10, Math.Abs(precision));
            value = value + (5 * precision / 10);
            return Math.Round(value - (value % precision), 0);
        }
    }

Example:

float value = F6666.677777;
Console.Write(value.Round(2)) // = 6666.68
Console.Write(value.Round(0)) // = 6667
Console.Write(value.Round(-2)) // = 6700 

Answer 4

Try this expression:

(n + 50) / 100 * 100

Answer 5

If you only want to round integer numbers up (as the OP actually did), then you can resort to this solution:

public static class MathExtensions
{
    public static int RoundUpTo(this int number, int nearest)
    {
        if (nearest < 10 || nearest % 10 != 0)
            throw new ArgumentOutOfRangeException(nameof(nearest), $"{nameof(nearest)} must be a positive multiple of 10, but you specified {nearest}.");

        int modulo = number % nearest;
        return modulo == 0 ? number : modulo > 0 ? number + (nearest - modulo) : number - modulo;
    }
}

If you want to perform floating-point (or decimal) rounding, then resort to the answers of @krizzzn and @Jim Aho.

Answer 6

int num = 9660;
int remainder = num % 100;
Console.WriteLine(remainder < 50 ? num - remainder : num + (100 -remainder));

Note: I haven't tested this thoroughly.