The Rule of 15

The Rule of 15 is a bridge bidding convention that is used in just one situation.  If you are the fourth player in a game of bridge AND you have fewer than 12 points AND no-one else has opened the bidding.

There are a total of 40 high card point (HCPs) in a game of bridge (four for each ace, three for each king, two for each queen and one for each jack).  As a general rule a player needs 12 or more points to open the bidding.  If no-one has opened you know that no-one else has 12+ points.  If you also have fewer than 12 points in your hand, you know that the points are fairly evenly distributed between the players.

If you are in a competitive situation you have to decide whether it would be more beneficial to pass and have the cards re-dealt or to open the bidding for your partnership.  How can you decide?

Imagine that we are West and the cards in our hand are as follows:

S: 10 9, H: K 7 3  2, D: A J 9 5 4,   C: K 6 2

The three previous players have all passed.  As you can see, we only have 11 points in our hand.  Should we pass too, or can we open the bidding?

If we do bid, we want to be fairly sure that the game will be played in our contract.  We know that neither side has enough points for game (25+) as we know that no-one else has 12+ points.  But if we open with a bid of 1 of a suit, there is the possibility of the opponents overcalling us at the one level, unless we can open the bidding with a bid of 1 spade.  The key to deciding is working out who has the spades.

This is where we use the Rule of 15.

We need to know if we have enough spades to open the bidding.  We do this by adding the number of HCPs that we hold to the number of spades in our hand.  If the total is 15 or more then we can open the bidding if we want to.

To see how this work, take a look at the following examples.  We’ll start with the hand that was shown above:

S: 10 9, H: K 7 3  2, D: A J 9 5 4,   C: K 6 2

We have 11 HCPs, but we only hold two spades.  The combined total is 13.  We don’t have enough spades so we should pass.  If we open in diamonds it is possible that we could be overcalled at the one level, allowing the opponents to play the game in the suit of their choice.

But what about this hand?

This hand also has 11 HCPs but it has one crucial difference.  Instead of 5 cards in diamonds it has 5 cards in spades.  Adding the two gives us a total of 16.  This means we can open the bidding in spades and we can’t be overcalled at the 1 level.

You can practice using the Rule of 15, and many other bridge bidding conventions, by joining No Fear Bridge for your two week, absolutely no obligation, trial.

Acol bridge players can join HERE.  American Standard bridge players can join HERE.