Converting file size in bytes to human-readable string

Question

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

function getReadableFileSizeString(fileSizeInBytes) {
    var i = -1;         


        

Answer 1

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.

Answer 2

A simple and short "Pretty Bytes" function for the SI system without the unnecessary fractionals rounding.

In fact, because the number size is supposed to be human-readable, a "1 of a thousand fraction" display is no longer human.

The number of decimal places is defaulted to 2 but can be modified on calling the function to other values. The common mostly display is the default 2 decimal place.

The code is short and uses the method of Number String Triplets.

Hope it is useful and a good addition to the other excellent codes already posted here.

// Simple Pretty Bytes with SI system
// Without fraction rounding

function numberPrettyBytesSI(Num=0, dec=2){
if (Num<1000) return Num+" Bytes";
Num =("0".repeat((Num+="").length*2%3)+Num).match(/.{3}/g);
return Number(Num[0])+"."+Num[1].substring(0,dec)+" "+"  kMGTPEZY"[Num.length]+"B";
}

console.log(numberPrettyBytesSI(0));
console.log(numberPrettyBytesSI(500));
console.log(numberPrettyBytesSI(1000));
console.log(numberPrettyBytesSI(15000));
console.log(numberPrettyBytesSI(12345));
console.log(numberPrettyBytesSI(123456));
console.log(numberPrettyBytesSI(1234567));
console.log(numberPrettyBytesSI(12345678));

Answer 3

Solution as ReactJS Component

Bytes = React.createClass({
    formatBytes() {
        var i = Math.floor(Math.log(this.props.bytes) / Math.log(1024));
        return !this.props.bytes && '0 Bytes' || (this.props.bytes / Math.pow(1024, i)).toFixed(2) + " " + ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'][i]
    },
    render () {
        return (
            <span>{ this.formatBytes() }</span>
        );
    }
});

UPDATE For those using es6 here is a stateless version of this same component

const sufixes = ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
const getBytes = (bytes) => {
  const i = Math.floor(Math.log(bytes) / Math.log(1024));
  return !bytes && '0 Bytes' || (bytes / Math.pow(1024, i)).toFixed(2) + " " + sufixes[i];
};

const Bytes = ({ bytes }) => (<span>{ getBytes(bytes) }</span>);

Bytes.propTypes = {
  bytes: React.PropTypes.number,
};

Answer 4

My answer might be late, but I guess it will help someone.

Metric prefix:

/**
 * Format file size in metric prefix
 * @param fileSize
 * @returns {string}
 */
const formatFileSizeMetric = (fileSize) => {
  let size = Math.abs(fileSize);

  if (Number.isNaN(size)) {
    return 'Invalid file size';
  }

  if (size === 0) {
    return '0 bytes';
  }

  const units = ['bytes', 'kB', 'MB', 'GB', 'TB'];
  let quotient = Math.floor(Math.log10(size) / 3);
  quotient = quotient < units.length ? quotient : units.length - 1;
  size /= (1000 ** quotient);

  return `${+size.toFixed(2)} ${units[quotient]}`;
};

Binary prefix:

/**
 * Format file size in binary prefix
 * @param fileSize
 * @returns {string}
 */
const formatFileSizeBinary = (fileSize) => {
  let size = Math.abs(fileSize);

  if (Number.isNaN(size)) {
    return 'Invalid file size';
  }

  if (size === 0) {
    return '0 bytes';
  }

  const units = ['bytes', 'kiB', 'MiB', 'GiB', 'TiB'];
  let quotient = Math.floor(Math.log2(size) / 10);
  quotient = quotient < units.length ? quotient : units.length - 1;
  size /= (1024 ** quotient);

  return `${+size.toFixed(2)} ${units[quotient]}`;
};

Examples:

// Metrics prefix
formatFileSizeMetric(0)      // 0 bytes
formatFileSizeMetric(-1)     // 1 bytes
formatFileSizeMetric(100)    // 100 bytes
formatFileSizeMetric(1000)   // 1 kB
formatFileSizeMetric(10**5)  // 10 kB
formatFileSizeMetric(10**6)  // 1 MB
formatFileSizeMetric(10**9)  // 1GB
formatFileSizeMetric(10**12) // 1 TB
formatFileSizeMetric(10**15) // 1000 TB

// Binary prefix
formatFileSizeBinary(0)     // 0 bytes
formatFileSizeBinary(-1)    // 1 bytes
formatFileSizeBinary(1024)  // 1 kiB
formatFileSizeBinary(2048)  // 2 kiB
formatFileSizeBinary(2**20) // 1 MiB
formatFileSizeBinary(2**30) // 1 GiB
formatFileSizeBinary(2**40) // 1 TiB
formatFileSizeBinary(2**50) // 1024 TiB

Answer 5

Another embodiment of the calculation

function humanFileSize(size) {
    var i = Math.floor( Math.log(size) / Math.log(1024) );
    return ( size / Math.pow(1024, i) ).toFixed(2) * 1 + ' ' + ['B', 'kB', 'MB', 'GB', 'TB'][i];
};

Answer 6

This is size improvement of mpen answer

function humanFileSize(bytes, si=false) {
  let u, b=bytes, t= si ? 1000 : 1024;     
  ['', si?'k':'K', ...'MGTPEZY'].find(x=> (u=x, b/=t, b**2<1));
  return `${u ? (t*b).toFixed(1) : bytes} ${u}${!si && u ? 'i':''}B`;    
}

function humanFileSize(bytes, si=false) {
  let u, b=bytes, t= si ? 1000 : 1024;     
  ['', si?'k':'K', ...'MGTPEZY'].find(x=> (u=x, b/=t, b**2<1));
  return `${u ? (t*b).toFixed(1) : bytes} ${u}${!si && u ? 'i':''}B`;    
}


// TEST
console.log(humanFileSize(5000));      // 4.9 KiB
console.log(humanFileSize(5000,true)); // 5.0 kB