Open-Raise Sizing: How Big to Raise Preflop

Your default open-raise should be 2.5x the big blind online and 3x live, plus one big blind for every limper already in the pot. That’s the whole answer for most spots. The deeper question — why smaller is usually better, when to deviate, and how position changes things — is what separates a size you copied from a size you understand.

Why smaller sizes won

Old-school advice was “raise 4x plus a limper.” Modern solvers and the shift to online 6-max cash pushed sizes down to 2–2.5x. The logic is pure risk-versus-reward:

• You’re trying to win the same 1.5 big blinds in the pot (the two blinds) whether you raise 2x or 4x.
• A smaller raise risks less to win that same prize, so it can be profitable with a wider range of hands.
• Against players who defend correctly, the smaller size doesn’t meaningfully change how often they fold — so you keep the fold equity while lowering your cost.

The main cost of going small is that you give opponents a slightly better price to call or 3-bet. In practice that’s a fair trade, which is why 2.2–2.5x is the online standard.

2.5x vs 3x vs a min-raise

There’s no single correct number — there’s a range of fine choices with different trade-offs.

Open size	Best for	Trade-off
Min-raise (2x)	6-max online, late position	Cheapest price offered to opponents; invites more flats and 3-bets
2.2–2.5x	Default online cash	Balanced risk/reward; the modern baseline
3x	Live cash, loose tables	Charges limpers/callers more; costs you more when it fails
3.5x+	Very loose live games	Thins the field, but bleeds chips when everyone folds

The looser and more passive the table, the larger you should open — big live games full of callers reward a 3x or bigger size because you get paid off. Tight, aggressive online tables reward smaller sizes.

Adjusting for limpers

Limpers add dead money and, more importantly, signal players who want to see a flop. Charge them:

Open size = your normal raise + 1 big blind per limper.

So over two limpers, a 3x live open becomes 3x + 2bb ≈ 5bb. This does two jobs: it makes it expensive for the limpers to continue with weak hands, and it isolates them so you play the pot heads-up with position and initiative. Isolating limpers well is a skill of its own — the sizing above is just the starting point.

A sizing chart by position

Position affects range width far more than it affects size, but there are small tendencies worth knowing:

Position	Online size	Live size	Note
UTG / MP	2.5x	3x	Tighter range; a hair larger is fine to discourage flats
CO / BTN	2–2.5x	2.5–3x	Small size lets you open wide cheaply and steal blinds
SB (vs BB only)	3x or limp-heavy mix	3x	Out of position postflop, so a larger raise or a limping strategy both work

Notice the small blind is the odd one out. Because you’re guaranteed to be out of position against the big blind, many solver strategies use either a larger open or a mixed limping range from the SB — the opposite of the “raise or fold” rule that governs every other seat.

A worked example

You’re on the button with a wide stealing range. It folds to you, both blinds are 100bb deep.

• You open 2.5x. Only two players can call, and a small size still folds out the bottom of their ranges most of the time.
• You risk 2.5bb to win the 1.5bb in blinds. Because the price is low, even hands like K-8 suited can open profitably here — the small size is what makes your wide button range work.

Now the cutoff limps in front of you instead. You raise 2.5x + 1bb = 3.5x to isolate. The extra big blind charges the limper and discourages the blinds from tagging along, so you take the flop heads-up with position.

Common sizing mistakes

• Sizing by hand strength. Big with aces, small with rags — the most readable pattern in poker. One size per seat.
• Copying a live 3x online. In a tight 6-max game, 3x is often just burning an extra half-blind. Go smaller.
• Forgetting to add for limpers. Opening your standard size over two limpers gives them a cheap, tempting price to call.
• Overthinking it. Within reason, being consistent matters more than being perfect. A steady 2.5x beats a “correct” size you apply randomly.

Where this fits

Sizing is one lever; the bigger decisions are which hands you open and from where. Build the ranges first in preflop opening ranges, understand how the seat you sit in changes everything over in the position hub, and see how the price you offer ties into the poker math behind every call. When someone re-raises your open, the next decision lives in 3-bet ranges — and the full framework starts back at the preflop strategy hub.