The ACBL Convention Charts govern bidding agreements. The Open and Open+ Charts are intended for events with no masterpoint limits. The Basic and Basic+ Charts are intended for limited master point events. The requirements for an opening bid vary depending on the chart governing the game.
| Chart | Requirements for a Natural Opening Bid |
| Basic | At least Average Strength. |
| Basic+ | At least Near-Average Strength. |
| Open or Open+ | At least Near-Average strength in 1st or 2nd seat. No strength requirement is specified for 3rd or 4th seat, but a Purely Destructive opening bid is not allowed. |
Average Strength is defined as "A hand that has at least 10 HCP or meets the 'Rule of 19'."
Near Average Strength is defined as "A hand that has at least 8 HCP or meets the 'Rule of 17'."
The Rule of 19 considers the length of a player's 2 longest suits. If the number of cards in a player's 2 longest suits plus their HCP are 19 or more, the player's hand meets the Rule of 19. A hand like ♠A76532 ♥8 ♦KQ ♣8742 has just 9 HCP, but meets the Rule of 19 because it has 10 cards in their 2 longest suits and has 9 HCP.
The Rule of 17 is similar, but has a threshold of 17. If the number of cards in a player's 2 longest suits plus their HCP are 17 or more, the player's hand meets the Rule of 17. A hand like ♠A76532 ♥8 ♦K8 ♣8742 has just 9 HCP, but meets the Rule of 17 because it has 10 cards in their 2 longest suits and has 7 HCP.
Click here to see the ACBL Convention Charts.
