Does .NET provide an easy way convert bytes to KB, MB, GB, etc.?

Question

Here is a fairly concise way to do this:

static readonly string[] SizeSuffixes = 
                   { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };
static string SizeSuffix(Int64 value, int decimalPlaces = 1)
{
    if (decimalPlaces < 0) { throw new ArgumentOutOfRangeException("decimalPlaces"); }
    if (value < 0) { return "-" + SizeSuffix(-value, decimalPlaces); } 
    if (value == 0) { return string.Format("{0:n" + decimalPlaces + "} bytes", 0); }

    // mag is 0 for bytes, 1 for KB, 2, for MB, etc.
    int mag = (int)Math.Log(value, 1024);

    // 1L << (mag * 10) == 2 ^ (10 * mag) 
    // [i.e. the number of bytes in the unit corresponding to mag]
    decimal adjustedSize = (decimal)value / (1L << (mag * 10));

    // make adjustment when the value is large enough that
    // it would round up to 1000 or more
    if (Math.Round(adjustedSize, decimalPlaces) >= 1000)
    {
        mag += 1;
        adjustedSize /= 1024;
    }

    return string.Format("{0:n" + decimalPlaces + "} {1}", 
        adjustedSize, 
        SizeSuffixes[mag]);
}

And here's the original implementation I suggested, which may be marginally slower, but a bit easier to follow:

static readonly string[] SizeSuffixes = 
                  { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };

static string SizeSuffix(Int64 value, int decimalPlaces = 1)
{
    if (value < 0) { return "-" + SizeSuffix(-value, decimalPlaces); } 

    int i = 0;
    decimal dValue = (decimal)value;
    while (Math.Round(dValue, decimalPlaces) >= 1000)
    {
        dValue /= 1024;
        i++;
    }

    return string.Format("{0:n" + decimalPlaces + "} {1}", dValue, SizeSuffixes[i]);
}

Console.WriteLine(SizeSuffix(100005000L));

One thing to bear in mind - in SI notation, "kilo" usually uses a lowercase k while all of the larger units use a capital letter. Windows uses KB, MB, GB, so I have used KB above, but you may consider kB instead.

Checkout the ByteSize library. It's the System.TimeSpan for bytes!

It handles the conversion and formatting for you.

var maxFileSize = ByteSize.FromKiloBytes(10);
maxFileSize.Bytes;
maxFileSize.MegaBytes;
maxFileSize.GigaBytes;

It also does string representation and parsing.

// ToString
ByteSize.FromKiloBytes(1024).ToString(); // 1 MB
ByteSize.FromGigabytes(.5).ToString();   // 512 MB
ByteSize.FromGigabytes(1024).ToString(); // 1 TB

// Parsing
ByteSize.Parse("5b");
ByteSize.Parse("1.55B");

I would solve it using Extension methods, Math.Pow function and Enums:

public static class MyExtension
{
    public enum SizeUnits
    {
        Byte, KB, MB, GB, TB, PB, EB, ZB, YB
    }

    public static string ToSize(this Int64 value, SizeUnits unit)
    {
        return (value / (double)Math.Pow(1024, (Int64)unit)).ToString("0.00");
    }
}

and use it like:

string h = x.ToSize(MyExtension.SizeUnits.KB);

Since everyone else is posting their methods, I figured I'd post the extension method I usually use for this:

EDIT: added int/long variants...and fixed a copypasta typo...

public static class Ext
{
    private const long OneKb = 1024;
    private const long OneMb = OneKb * 1024;
    private const long OneGb = OneMb * 1024;
    private const long OneTb = OneGb * 1024;

    public static string ToPrettySize(this int value, int decimalPlaces = 0)
    {
        return ((long)value).ToPrettySize(decimalPlaces);
    }

    public static string ToPrettySize(this long value, int decimalPlaces = 0)
    {
        var asTb = Math.Round((double)value / OneTb, decimalPlaces);
        var asGb = Math.Round((double)value / OneGb, decimalPlaces);
        var asMb = Math.Round((double)value / OneMb, decimalPlaces);
        var asKb = Math.Round((double)value / OneKb, decimalPlaces);
        string chosenValue = asTb > 1 ? string.Format("{0}Tb",asTb)
            : asGb > 1 ? string.Format("{0}Gb",asGb)
            : asMb > 1 ? string.Format("{0}Mb",asMb)
            : asKb > 1 ? string.Format("{0}Kb",asKb)
            : string.Format("{0}B", Math.Round((double)value, decimalPlaces));
        return chosenValue;
    }
}