How much to open, online and live

What the size of your open changes (the blinds' price, who calls, the SPR) and how to adjust it for limpers, antes and live games.

In this lesson

Explain how open size changes the blinds' price, the calling ranges and the SPR.
Work out how often a steal has to work at a given size.
Add to your open for each player who has already limped.
Adjust your size for antes, straddles and looser live tables.

Read first: Seats and opening ranges, 6-max and full ring · Advice, not a lock: every lesson opens.

Concepts used: Raise first in (RFI), Stealing the blinds, SPR and commitment

Three things the size changes

The size of your open is not just a habit. It sets three numbers at once: how often your open has to win the blinds straight away, what price the big blind gets to call, and how big the pot is when the flop comes.

Each of them pulls in a different direction, which is why there is no single right size for every table. What there is, is a clear trade-off you can work out on a napkin.

Your side: bigger opens need more folds

An open risks its size to win the 1.5 bb of blinds. The break-even fold rate is the open divided by the open plus the blinds:

2 bb: 2 / 3.5 ≈ 57.1%.
2.5 bb: 2.5 / 4 = 62.5%.
3 bb: 3 / 4.5 ≈ 66.7%.
4 bb: 4 / 5.5 ≈ 72.7%.

Doubling the open from 2 bb to 4 bb does not double what you win when they fold; it is still 1.5 bb. It only raises what you lose every time someone plays back.

Blinds and antes in the middle1.5 bb

Your open (chips risked)2.5 bb

How often they fold60%

Alpha: folds needed: 62.5%
EV if it never wins when called: -0.1 bbLosing

Move the open size and watch the break-even fold rate climb. Add antes to the blinds and watch it fall.

The big blind's side: bigger opens give a worse price

When the small blind folds, the big blind calls the open minus the 1 bb it already posted, into a pot of the open plus 1.5 bb. Against 2 bb it calls 1 into 3.5 and needs 1 / 4.5 ≈ 22.2%. Against 2.5 bb it calls 1.5 into 4 and needs about 27.3%. Against 4 bb it calls 3 into 5.5 and needs about 35.3%.

So a bigger open folds out more of the blinds' weak hands. That is the case for it. The case against is that the hands which continue are stronger, and you have paid more to find out.

"I open 12 bb and nobody calls"

A 12 bb open has to win the blinds 12 / 13.5 ≈ 88.9% of the time to break even as a steal. When everyone folds you win 1.5 bb. When someone continues, they hold a hand that is happy to play a big pot, and your weaker opens are in trouble.

That is the problem with huge opens: you win small when they fold and lose big when they do not. If nobody ever calls, the size is not working; it is just making every mistake expensive.

The pot you take to the flop

Size also sets the stack-to-pot ratio. Open 2.5 bb at 100 bb and the big blind calls: the pot is 2.5 + 2.5 + 0.5 = 5.5 bb with 97.5 bb behind, an SPR of about 17.7. Open 4 bb instead and the pot is 8.5 bb with 96 bb behind, an SPR of about 11.3.

Pot5.5 bb

Effective stack97.5 bb

Streets to bet3 streets

SPR: 17.7
Geometric bet each street: 115.8% of the pot · 6.37 bb
Called pot-sized bets the stacks hold: 3.3

Change the pot to see how the open size moves the SPR, and how many pot-sized bets it takes to get the stacks in.

A lower SPR makes one strong pair easier to play for stacks. That suits a range full of big cards, which is one reason players with value-heavy ranges like larger opens.

Online, live, and when to change

Rail's charts open to 2.5 bb from UTG to the button and 3 bb from the small blind at 100 bb, and 2.2 bb at 40 bb. Those are sound defaults for raked online games, where the blinds fight back.

Live pools call far more often. Against players who call almost any open, a bigger size with a range weighted toward strong hands wins more when called. A 5 bb open needs 5 / 6.5 ≈ 76.9% folds as a pure steal, but against players who call too much you are not stealing; you are charging them.

Behind limpers, add about 1 bb for each limper. That is an isolation raise, and it has its own lesson.
Antes add dead money: the same open needs fewer folds, so you can open smaller and wider.
A straddle doubles the big blind; scale every size with it. Rail does not analyse straddled pots yet.

Rules of thumb

Bigger opens need more folds and give the big blind a worse price: 2.5 bb needs 62.5% folds and gives the big blind about 27.3%.
When nobody calls your opens, the size is too big, not perfect.
Bigger opens lower the SPR, which suits value-heavy ranges.
Live, against players who call too much, size up with a stronger range rather than steal wide.

When they break

With antes or a straddle the dead money changes, so the online defaults no longer fit as they are.
Against blinds who 3-bet a lot, a smaller open loses less each time it is attacked.

Example hands

Examples come from two places only: your own analysed hands in this lesson's spots, and a hand Rail deals and grades itself. Never a hand from outside Rail.

From your own hands

Practice

The lesson is mastered when every exercise below that Rail can grade is passed. Missed items come back later as review cards.

Exercise 1

Pass: 5 of 6 right

Six opens of different sizes into 1.5 bb of blinds. Work out how often everyone must fold for a pure steal to break even before the calculator shows it.

Pass: 5 of 6 right

Six opens, the small blind folds. Work out the equity the big blind needs to call before the calculator shows it.

Exercise 3

Optional

Your own unopened decisions where the analysis found the costliest mistakes. Decide before you see what you did.