Quick mental math for odds
The Rule of 2 and 4 is the fastest way to estimate your equity at the table. Instead of doing complex probability math, you simply multiply your number of outs by a small number.
On the flop with two cards to come, multiply your outs by 4. On the turn with one card to come, multiply your outs by 2. The result is your approximate percentage chance of hitting your draw.
Each unseen card represents roughly a 2% chance per card to come. On the flop, with two cards still to be dealt (turn and river), each out gives you about 4% equity. On the turn, with only one card left, each out gives you about 2%.
Examples
Flush draw on the flop (9 outs)
9 outs x 4 = ~36% chance by the river
Open-ended straight on the turn (8 outs)
8 outs x 2 = ~16% chance on the river
Gutshot on the flop (4 outs)
4 outs x 4 = ~16% chance by the river
Memorize these common scenarios and you will rarely need to calculate at the table. The Rule of 2 and 4 is slightly less accurate with higher out counts, but it is close enough for fast decisions.
You have 9 outs on the flop. Using the Rule of 4, what is your approximate equity?
You have 4 outs on the turn. Using the Rule of 2, what is your approximate equity?
Answer all quiz questions correctly to complete this lesson and earn XP.