using System;

​

namespace ConsoleApp1

{

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine(convertBytes(435));                 // 435 bytes

            Console.WriteLine(convertBytes(3398));                // 3.3 KB

            Console.WriteLine(convertBytes(490398));              // 479 KB

            Console.WriteLine(convertBytes(6544528));             // 6.2 MB

            Console.WriteLine(convertBytes(23483023));            // 22 MB

            Console.WriteLine(convertBytes(3984578493));          // 3.7 GB

            Console.WriteLine(convertBytes(30498505889));         // 28 GB

            Console.WriteLine(convertBytes(9485039485039445));    // 8.4 PB

            Console.ReadLine();

        }

​

        public static string convertBytes(decimal? x, int l = 0)

        {

            for (l = 0; x >= 1024;)

            {

                l++;

                x = x / 1024;

            }

​

            string[] units = { "Bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };

            string format = x < 10 && l > 0 ? "{0:0.#}" : "{0:0}";

​

            return String.Format(format, x) + " " + units[l];

        }

    }

}

​