Note: Credit goes to JoeyT2008 for creating the code, minor changes made by myself after numerous false edits by the member Anthony, apparently this script was stolen from Anthony however the dates of creation say otherwise.
Steam Community ID Converter:
Input a Steam ID or a Steam Community ID and it will be converted.
STEAMID to STEAMCOMMUNITYID:
STEAM_0:1:12280641 = 12280641 * 2 + 1 + 76561197960265728 = 76561197984827011.
Url = http://steamcommunity.com/profiles/76561197984827011
STEAMCOMMUNITYID to STEAMID:
76561197984827011 - 1 / 2 = 12280641 = STEAM_0:1:12280641