javascriptfilesizehuman-readable

Converting file size in bytes to human-readable string

I'm using this function to convert a file size in bytes to a human-readable file size:

function getReadableFileSizeString(fileSizeInBytes) {
  var i = -1;
  var byteUnits = [' kB', ' MB', ' GB', ' TB', 'PB', 'EB', 'ZB', 'YB'];
  do {
    fileSizeInBytes /= 1024;
    i++;
  } while (fileSizeInBytes > 1024);

  return Math.max(fileSizeInBytes, 0.1).toFixed(1) + byteUnits[i];
}

console.log(getReadableFileSizeString(1551859712)); // output is "1.4 GB"

However, it seems like this isn't 100% accurate. For example:

getReadableFileSizeString(1551859712); // output is "1.4 GB"

Shouldn't this be "1.5 GB"? It seems like the division by 1024 is losing precision. Am I totally misunderstanding something or is there a better way to do this?

Solution

  • It depends on whether you want to use the binary or decimal convention.

    RAM, for instance, is always measured in binary, so to express 1551859712 as ~1.4GiB would be correct.

    On the other hand, hard disk manufacturers like to use decimal, so they would call it ~1.6GB.

    And just to be confusing, floppy disks use a mixture of the two systems - their 1MB is actually 1024000 bytes.