C# Get the readable filesize of Int32/Int64 value

/// get file size from Int32 / In64 value.

public static string ToFileSize(this int source)
{
    return ToFileSize(Convert.ToInt64(source));
}
public static string ToFileSize(this long source)
{
    const int byteConversion = 1024;
    double bytes = Convert.ToDouble(source);

    if (bytes >= Math.Pow(byteConversion, 3)) //GB Range
    {
        return string.Concat(Math.Round(bytes / Math.Pow(byteConversion, 3), 2), " GB");
    }
    else if (bytes >= Math.Pow(byteConversion, 2)) //MB Range
    {
        return string.Concat(Math.Round(bytes / Math.Pow(byteConversion, 2), 2), " MB");
    }
    else if (bytes >= byteConversion) //KB Range
    {
        return string.Concat(Math.Round(bytes / byteConversion, 2), " KB");
    }
    else //Bytes
    {
        return string.Concat(bytes, " Bytes");
    }
}