EditorUtility.FormatBytes

public static string FormatBytes (int bytes);

Description

Returns a text for a number of bytes.

using UnityEngine;
using UnityEditor;

public class FormatBytesExample : MonoBehaviour
{
	void Start( )
	{
		// prints "100 bytes"
		print( EditorUtility.FormatBytes( 100 ) );

		// prints "2.0 KB"
		print( EditorUtility.FormatBytes( 2048 ) );
	}
}