The mistakes that cost you the most
Optimal play holds the edge near 2.19%. Every mistake below quietly pushes it up — and the two most common ones cost the most.
Short answer
The costliest mistakes, in order: checking hands that should raise 4x pre-flop, raising late (2x or 1x) when 4x was available, folding rivers you should bet, and misreading a board pair as your own. All four bleed EV; the explorer on the EV page lets you price any of them.
1. Playing too passively pre-flop
This is the big one. Correct play raises 4x with about 37.7% of deals, including every ace and every pair 33 and up. Checking those hands to “see a cheaper flop” throws away the biggest edge in the game. When the chart says raise 4x, raise 4x.
2. Raising late instead of early
Your maximum bet shrinks from 4x pre-flop to 2x on the flop to 1x on the river. Slow-playing a raising hand does not save money — it caps how much you can win with your edge intact.
3. Over-folding the river
Folding forfeits your Ante and Blind (an EV near −2 units). You should bet 1x on the river almost always, folding only when the dealer’s scare outs cross the threshold. See the exact boundary on the 21-outs page.
4. Misreading the board
A pair lying entirely on the board is shared with the dealer — it is not your pair and is no reason to raise the flop. A raise needs a hidden pair, one that uses at least one of your hole cards. Confusing the two leads to raising junk and checking value.
See the cost yourself
Load a marginal spot in the explorer and compare the right play against the tempting wrong one. The gap between the bars is exactly what the mistake costs, per hand.
Common questions
What single change helps most?
Raise 4x every time the pre-flop chart says so. Passive pre-flop play is the most expensive habit, and fixing it recovers most of the lost EV on its own.
Is folding ever right?
Yes, but only on the river and only when the dealer’s outs to beat you are large enough. Elsewhere there is no fold — you check for free instead.
How much do mistakes really cost?
Enough to multiply the 2.19% edge several times over in a careless session. Use the EV explorer above to price the specific error you are worried about.