Poker Math · 2
Outs and Equity (Rule of 4 and 2)
Mental math for estimating your chance to make a draw. The fastest tool in your kit.
Formula
Equity ≈ Outs × 4 (flop, by river) Equity ≈ Outs × 2 (next street only)
Explanation
An "out" is any card that improves you to a winning hand. Multiply outs by 4 to estimate equity by the river (two streets to come), or by 2 for just the next card. This rule is slightly optimistic for 8+ outs but accurate enough for in-game decisions.
Example
Setup
You have a flush draw on the flop. Two cards to come.
Calculation
- Flush draw = 9 outs (13 cards of your suit − 4 you can see)
- Rule of 4: 9 × 4 = 36%
- Actual: 35% (rule is very close here)
Conclusion
You have roughly 36% to make your flush by the river.
Setup
You have an open-ended straight draw on the turn. One card to come.
Calculation
- Open-ended = 8 outs
- Rule of 2 (one street): 8 × 2 = 16%
- Actual: 17% (very close)
Conclusion
You have about 16% to hit on the river.
Practice
You have a gutshot straight draw (4 outs) on the flop. Roughly what is your equity by the river?