What is the rule of 4 and 2?
The rule of 4 and 2 in Texas Hold’em poker is a shortcut estimation of how likely the next card dealt will complete your draw.
You can use this estimate to work out if it is mathematically ‘worth’ calling a bet.
Where did the rule come from?
Whilst not entirely sure where the rule originated, it is fair to say that it was popularized by Phil Gordon in his books and instructional videos.
How does the rule of 4 and 2 actually work?
After the ‘flop’ (first 3 community cards) has been dealt, you can use the rule to estimate the percentage chance of catching a card that completes your draw on the next street (the ‘turn’).
Multiply your ‘outs’ (the cards that will help you) by 2.
If after the flop, your opponent is ‘all-in’ then you are guaranteed to see the next two community cards (the ‘turn’ and the ‘river’), so you can multiply your ‘outs’ by 4.
Ignoring the tournament dynamics, if the percentage chance of you completing your draw is greater than the percentage of the pot your call would be, then you should call.
Let's explain using an example..
You have the Ace and King of spades, and the Three and Nine of spades have come down on the flop. You have a ‘nut’ flush draw and it will be the winning hand a great deal of the time.
There is $80 in the pot and your opponent bets $10. Should you call?
A call will cost you $10 to potentially win a pot of $100 ($80 + $10 bet + $10 call).
Your call would be 10% of the $100 pot.
Using the rule of 4 and 2, you multiply your 9 ‘outs’ (the remaining spades in the deck) by 2 to get an estimated 18% chance of hitting your nut flush.
In this instance, your percentage chance of catching a spade on the turn (18%) is greater than your percentage contribution to the pot (10%).
Using the rule of 4 and 2, a call is warranted.
How reliable is the rule of 4 and 2?
Whilst the rule is useful for a quick calculation in your head at the table, it does break down if you have a large number of outs e.g. 15.
However, you’re likely to get amongst the action anyway if you have that many outs!
May your outs be many, and your bad beats few!