Here's a code sample to turn any number into a human-readable size in bytes, in Flex.

Enjoy!

 
 package com.yourapp.lib.utils 
 { 
 import com.yourapp.lib.utils.MathUtils; 
 
 public class NumberUtils 
 { 
 public static const GIGABYTE:Number = 1073741824; 
 
 private static const _formats:Array = [ 
 "Bytes", 
 "KB", 
 "MB", 
 "GB", 
 "TB" 
 ]; 
 
 private static const _sizes:Array 	= [ 
 1, 
 1024, 
 1048576, 
 1073741824, 
 1099511627776 
 ]; 
 
 public static function humanSize(value:Number, digits:int=1):String { 
 if (value == 0) { 
 return "0 Bytes"; 
 } 
 
 for (var i:Number = _sizes.length; i >= 0; i--) { 
 if (value >= _sizes[i]) { 
 break; 
 } 
 } 
 
 return MathUtils.round(value / _sizes[i], digits) + " " + _formats[i]; 
 } 
 } 
 
 } 
 
 package com.yourapp.lib.utils 
 { 
 public class MathUtils 
 { 
 public static function round(value:Number, decimals:int = 0):Number { 
 var rounder:Number = Math.pow(10, decimals); 
 return Math.round(value * rounder) / rounder; 
 } 
 
 } 
 
 }