Page "Contract bridge" Paragraph 11

Within any level of bidding ( i. e. from one to seven ), suit rank establishes the bid ’ s rank, i. e. a bid of two diamonds outranks a bid of two clubs, a bid of three spades outranks a bid of three hearts, a bid of three notrump outranks a bid of three spades.

Thus, there are 35 possible basic contracts ( five at each of the seven levels ); 1 being the lowest, followed by 1 etc., up to 7NT, the highest possible bid.