Rule of 4 and 2
The Rule of 4 and 2 is a table-speed approximation: multiply outs by about four with two cards to come, or by about two with one card to come. Exact probability uses combinations and diverges as outs increase.
What you will be able to do
- Choose ×4 only when two cards remain and both will be seen.
- Choose ×2 when exactly one card remains.
- Label the shortcut as an approximation and recognize its limits.
POKER CONSEQUENCE
Calculate how Rule of 4 and 2 changes the decision
A nine-out flush draw on the flop is roughly 36% to improve by the river using 9×4, while the exact at-least-once probability is about 35.0%. On the turn, 9×2 gives 18% versus exactly 9/46 ≈ 19.6%.
QUICK ESTIMATE VERSUS EXACT PROBABILITY
The Rule of 4 and 2 is a table shortcut
Multiplying your outs by four or two gives a fast mental estimate—not the exact probability. Use the comparison below to see how close the shortcut is.
- Unseen cards
- 47
- Outs
- 9
- Cards to come
- 2
9 × 4 = 36%
1 − (38/47 × 37/46) = 35.0%
A small difference makes the shortcut useful at the table.
On the flop, you can see two hole cards and three board cards, leaving 47 unseen cards. With two cards to come, multiply the outs by four.
ONE THING TO REMEMBER
Do not use ×4 for a flop decision that may face another bet before the river as though seeing both cards were guaranteed.
TRY IT
This is a 2-question test. Start when you are ready.