Format Bytes to Kilobytes, Megabytes, Gigabytes

function formatBytes(bytes, decimals = 2) {
    if (!+bytes) return '0 Bytes'

    const k = 1024
    const dm = decimals < 0 ? 0 : decimals
    const sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']

    const i = Math.floor(Math.log(bytes) / Math.log(k))

    return `${parseFloat((bytes / Math.pow(k, i)).toFixed(dm))} ${sizes[i]}`
}

// Demo code
document.body.innerHTML += `<input type="text" oninput="document.querySelector('p').innerHTML=formatBytes(this.value)" value="1000"><p>1000 Bytes</p>`

How can I convert byte size into a human-readable format in Java?

Fun fact: The original snippet posted here was the most copied Java snippet of all time on Stack Overflow, and it was flawed. It was fixed, but it got messy.

Full story in this article: The most copied Stack Overflow snippet of all time is flawed!

Source: Formatting byte size to human readable format | Programming.Guide

SI (1 k = 1,000)

public static String humanReadableByteCountSI(long bytes) {
    if (-1000 < bytes && bytes < 1000) {
        return bytes + " B";
    }
    CharacterIterator ci = new StringCharacterIterator("kMGTPE");
    while (bytes <= -999_950 || bytes >= 999_950) {
        bytes /= 1000;
        ci.next();
    }
    return String.format("%.1f %cB", bytes / 1000.0, ci.current());
}

Binary (1 Ki = 1,024)

public static String humanReadableByteCountBin(long bytes) {
    long absB = bytes == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(bytes);
    if (absB < 1024) {
        return bytes + " B";
    }
    long value = absB;
    CharacterIterator ci = new StringCharacterIterator("KMGTPE");
    for (int i = 40; i >= 0 && absB > 0xfffccccccccccccL >> i; i -= 10) {
        value >>= 10;
        ci.next();
    }
    value *= Long.signum(bytes);
    return String.format("%.1f %ciB", value / 1024.0, ci.current());
}

Example output:

                             SI     BINARY

                  0:        0 B        0 B
                 27:       27 B       27 B
                999:      999 B      999 B
               1000:     1.0 kB     1000 B
               1023:     1.0 kB     1023 B
               1024:     1.0 kB    1.0 KiB
               1728:     1.7 kB    1.7 KiB
             110592:   110.6 kB  108.0 KiB
            7077888:     7.1 MB    6.8 MiB
          452984832:   453.0 MB  432.0 MiB
        28991029248:    29.0 GB   27.0 GiB
      1855425871872:     1.9 TB    1.7 TiB
9223372036854775807:     9.2 EB    8.0 EiB   (Long.MAX_VALUE)

Converting bytes to kilobytes/megabytes

Use FORMAT if you want to have a specified significant number of decimal values in MB. N3 here is for showing 3 decimal numbers.

(CASE WHEN D.DocumentSize < 1000000 THEN
           CONCAT(CEILING(D.DocumentSize / 1024.0), 'KB')
      ELSE 
           CONCAT(FORMAT(D.DocumentSize / 1048576.0, 'N3'), 'MB')
 END) AS DocumentSizeText

PHP filesize MB/KB conversion

Here is a sample:

<?php
// Snippet from PHP Share: http://www.phpshare.org

    function formatSizeUnits($bytes)
    {
        if ($bytes >= 1073741824)
        {
            $bytes = number_format($bytes / 1073741824, 2) . ' GB';
        }
        elseif ($bytes >= 1048576)
        {
            $bytes = number_format($bytes / 1048576, 2) . ' MB';
        }
        elseif ($bytes >= 1024)
        {
            $bytes = number_format($bytes / 1024, 2) . ' KB';
        }
        elseif ($bytes > 1)
        {
            $bytes = $bytes . ' bytes';
        }
        elseif ($bytes == 1)
        {
            $bytes = $bytes . ' byte';
        }
        else
        {
            $bytes = '0 bytes';
        }

        return $bytes;
}
?>

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

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.

How do I quickly convert the size element of file.info() from bytes to KB, MB, GB, etc.?

The object.size() function does this type of formatting for it's results, but its meant to tell you the size of the R object you pass to it. It is not set up to take an arbitrary by value.

However, we can "steal" some of it's formatting logic. You can call it with

utils:::format.object_size(60963, "auto")
# [1] "59.5 Kb"

In that way we can call the un-exported formatting function. You can bring up the additional formatting options on the ?format.object_size help page. Note that it uses the rule that 1 Kb = 1024 bytes (not 1000 as in your example).

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