What Is a 4-Bet in Poker? Ranges, Sizing and the Math

"4-bet" sounds like jargon designed to confuse beginners, and the numbering really is confusing — a 4-bet is only the third raise anyone actually makes. Once you see where the count starts it never puzzles you again, and the rest of this page is the part that matters: how big, with what, and how often it has to work.

Why it's called a 4-bet

The count includes the big blind. It is a forced bet, but it is still money in the pot that everyone else has to match, so it is bet number one:

#	Action	What it means
Bet 1	The big blind	A forced bet, but still a bet. This is why the numbering feels off by one.
Bet 2	The open-raise	The first voluntary raise. Almost nobody calls it a '2-bet'.
Bet 3	The 3-bet	The re-raise over the open.
Bet 4	The 4-bet	The re-raise over the 3-bet — this article.
Bet 5	The 5-bet	At 100bb, nearly always all-in.

So: someone raises, someone 3-bets, and if the original raiser raises again, that is the 4-bet. Postflop the numbering resets — there is no blind to count, so the first bet is a bet, the raise is a raise, and nobody says "3-bet the flop" unless they are being precise about a re-raise.

Sizing: how often the 4-bet has to work

A 4-bet is a big lever. Because it is the third raise, it grows fast — and because it puts roughly a fifth of a 100bb stack in the middle, folding to a 5-bet afterwards is expensive. The right size is the one that charges the 3-bettor without committing you. Here is the pure fold-equity math for the standard sizings — the percentage is how often the 4-bet must simply end the hand to break even, ignoring all the times you get called and win:

Sequence (100bb, 0.5/1 blinds)	Size	You risk	To win	Break-even folds
CO opens 2.5 → BTN 3-bets 8 → CO 4-bets 18	2.25x	15.5bb	9.5bb	62.0%
CO opens 2.5 → BTN 3-bets 8 → CO 4-bets 21	2.6x	18.5bb	9.5bb	66.1%
BTN opens 2.5 → BB 3-bets 11 → BTN 4-bets 23	2.1x	20.5bb	11.5bb	64.1%
BTN opens 2.5 → BB 3-bets 11 → BTN 4-bets 25	2.3x	22.5bb	11.5bb	66.2%
CO opens 2.5 → BTN 3-bets 8 → CO shoves 100	all-in	97.5bb	9.5bb	91.1%

Two lessons fall out. First, smaller 4-bets need less fold equity — 18bb needs 62.0% folds where 21bb needs 66.1% — which is why modern sizing drifted down from the old 3x standard. Second, look at the last row: shoving 100bb over an 8bb 3-bet needs folds 91.1% of the time. Nobody folds that often, so a preflop jam at 100bb is a value play or nothing. Deep stacks reward the small 4-bet; short stacks flip that (see the tournament note below).

Which hands to 4-bet

Both ranges below are the site's published preflop ranges from the range library, with combos counted against the 1,326 possible starting hands:

Range	Hands	Combos	% of hands
4-bet, value only	AA, KK, AKs	16	1.2%
4-bet, mixed	AA, KK, QQ, AKs, AKo + A5s, A4s	42	3.2%
…for scale: 3-bet vs UTG (value)	AA, KK, QQ, AKs, AKo	34	2.6%
…for scale: 3-bet vs BTN (wide)	TT+, AJs+, KJs+, AQo+ and blocker bluffs	110	8.3%

The mixed range is 34 value combos to 8 bluff combos — 4.3 value hands for every bluff. That ratio is deliberately value-heavy because a 4-bet gets called by a range that is itself extremely strong; there is no room for the 2:1 balance you might use on a river. Pick the version that matches your opponent:

✓ Value-only (AA/KK/AKs) at the micros. Players who never 5-bet bluff hand you a free read: if they put in a fifth of their stack, they have it. Bluffing into that is lighting money on fire, and there is no penalty for being "unbalanced" against someone not looking.
✓ Mixed range against regs who 3-bet wide. Once an opponent 3-bets 8%+ of hands, a value-only 4-bet range means folding your entire opening range apart from the top 1.2% — an enormous, exploitable surrender. That is the moment A5s and A4s earn their seat.
✓ Add QQ and JJ only with a reason. QQ has 40.2% against the range that continues — value against a loose 3-bettor, a bluff-catcher against a nit. JJ is usually a call, not a 4-bet: it blocks none of the hands that beat it.

Why A5s and A4s are the bluffs

The continuing range against a 4-bet — call it QQ+/AK — is 34 combinations. Which hand you hold changes how many of those 34 your opponent can still have. This is exact counting, not estimation:

You hold	QQ+/AK combos left	Reduction	Aces left (of 6)
A5s / A4s	27	−21%	3
AKo	21	−38%	3
KQs	24	−29%	6
QQ	29	−15%	6
JJ	34	0%	6

A5s does the one job that matters most: it halves the aces, from 6 combos to 3, and cuts AK from 16 to 12. And unlike a pure air bluff it retains real equity when the plan fails — 30.2% against that whole range, with nut-flush and wheel-straight outs that are never dominated. JJ, by contrast, blocks nothing at all, which is exactly why it is a calling hand rather than a 4-bet bluff. That is blocker logic in its cleanest form — combinatorics applied to the two cards in your hand. Build and count your own versions in the range builder or the range explorer.

How each hand actually runs when called

Fold equity is only half of a 4-bet. Here is what happens on the times you get called — equity against the full QQ+/AK continuing range, simulated with the site's own evaluator over 3,000,000 trials per hand with card removal applied:

Hand	Equity vs QQ+/AK	Role	Note
AA	84.1%	Value	The reason the range exists.
KK	57.2%	Value	Still ahead even when only QQ+/AK continues.
AKs	41.9%	Value	Clears the 39.2% needed to call a 5-bet shove.
QQ	40.2%	Thin value	Value against loose 3-betters, a bluff-catcher against tight ones.
AKo	38.8%	Value	Lands just under the 5-bet-calling threshold — a real decision, not an auto-call.
JJ	36.2%	Usually call	Blocks nothing in the range. Flatting keeps the dominated hands in.
A5s	30.2%	Bluff	Halves the aces and still makes nut flushes and wheels.
A4s	29.8%	Bluff	Same blockers, marginally less straight equity.
AQs	28.6%	Fold / call	Dominated by most of the range — the classic 4-bet trap hand.

Note the gap between AKs (41.9%) and AQs (28.6%). AK is the hand the whole 4-bet structure is built around; AQ looks similar and is dominated by most of the range it runs into. Test any of these against your own range assumptions in the range equity calculator or a single matchup in the odds calculator.

Facing a 4-bet: call, 5-bet, or fold

When your 3-bet gets 4-bet, the pot is offering you a specific price. Two of the sequences from the table above, worked out:

• You 3-bet to 11bb from the big blind, villain 4-bets to 25bb. Calling costs 14bb into a final pot of 50.5bb — you need 27.7% equity to continue.
• You 3-bet to 8bb on the button, villain 4-bets to 21bb. Calling costs 13bb into 43.5bb — 29.9%.
• You 4-bet to 21bb and villain 5-bet shoves 100bb. Calling costs 79bb into 201.5bb — 39.2%. AKs clears it at 41.9%; AKo does not at 38.8%.

Those percentages assume no further betting, which is the honest way to read them: a call preflop is a commitment to play a 40bb+ pot out of position often enough that raw pot odds understate the difficulty. The practical hierarchy against an unknown 4-bettor at 100bb is to 5-bet AA/KK, call with AKs/QQ/JJ if you are getting a normal price, and fold the rest of your 3-betting range without agonising — including the suited-ace bluffs, which did their job the moment they got folds and cost you nothing extra when they don't.

The one leak this page exists to prevent

4-betting hands that are strong but dominated — AQ, AJs, TT — because they "feel like" premiums. Against a range that only continues with QQ+/AK, AQs has 28.6% equity. The 4-bet folds out everything you beat and gets called by everything that beats you. Either 4-bet the hands that want the money in, or bluff with the hands that block the calls; the middle is where stacks go to die.

Short stacks and tournaments: the 4-bet becomes a shove

Everything above assumes 100bb. Shrink the stack and the arithmetic inverts: at 40bb a 21bb 4-bet is already half your chips, so the non-committing 4-bet stops existing and the choice becomes shove or fold. Below roughly 25bb, 4-betting all-in is standard with your value range because there is nothing left to fold to. The baseline shove ranges by stack depth are on the push/fold chart (a Nash approximation — the tool page carries its accuracy note), and the stage-by-stage picture is in tournament strategy. Add ICM on a bubble and the calling ranges tighten further still, which makes the light 4-bet shove better, not worse.

Where these numbers come from

• Combo counts and blockers: exact counting against the C(52,2) = 1,326 starting combinations, using the site's published preflop ranges (app/lib/range-library.js — the data behind the range library).
• Break-even folds and pot odds: closed-form pot arithmetic. Break-even folds = risk / (risk + reward); pot odds = call / final pot. The full sequence and blind structure is printed beside every row so the arithmetic is checkable.
• Equities: Monte Carlo with the site's own 7-card evaluator (app/lib/poker-eval.js — the engine behind the odds calculator), 3,000,000 trials per hand against the QQ+/AK range with card removal applied and ties split. Standard error ≈ 0.03 percentage points.
• What this is not: solver output. The ranges are our published preflop ranges and the "QQ+/AK continues" assumption is a stated modelling choice, not a solved equilibrium. Change the continuing range and every equity above moves.

Common questions

What is a 4-bet in poker?

A 4-bet is the fourth bet in a preflop betting sequence — in practice, the re-raise of a 3-bet. The count starts with the big blind, which is bet number one. The first raise (the 'open') is bet two, the re-raise over it is the 3-bet, and the raise over that is the 4-bet. At 100bb a 4-bet usually commits about a fifth of your stack, so it is close to a decision to play for everything.

How big should a 4-bet be?

Roughly 2.2-2.5x the 3-bet when you have position, and a little larger when you don't — big enough to charge the 3-bettor, small enough that folding to a 5-bet still leaves you a stack. Worked example: you open the cutoff to 2.5bb, the button 3-bets to 8bb, you 4-bet to 21bb. You are risking 18.5bb more to win the 9.5bb already out there, so the 4-bet needs to end the hand 66.1% of the time to break even on fold equity alone. Trim it to 18bb and that drops to 62.0%.

What hands should you 4-bet?

Our published range library uses two versions. The value-only 4-bet range is AA, KK and AKs — 16 of the 1,326 possible starting combinations, or 1.2% of hands. That is the right default against players who never 5-bet bluff, which describes most of the micros. The mixed range adds QQ and AKo for value plus A5s and A4s as bluffs: 42 combos (3.2% of hands), a 4.3-to-1 value-to-bluff ratio.

Why is A5s a 4-bet bluff?

Card removal. Against a QQ+/AK range — the 34 combinations that typically continue against a 4-bet — holding A5s leaves only 27 of them, a 21% cut, and it specifically halves the aces (6 combos down to 3) and takes AK from 16 to 12. On top of that it is not drawing dead when called: simulated with our own evaluator over 3,000,000 trials, A5s has 30.2% equity against that exact range, versus 36.2% for JJ, a hand that blocks nothing at all. Blocking the hands that beat you and retaining nut-flush and wheel-straight potential is exactly what a bluff 4-bet should do.

Should you call or fold AK to a 4-bet?

At 100bb, call — and against most 4-bet sizings you can 5-bet AKs. The pot odds are precise: after you 3-bet to 11bb and face a 25bb 4-bet, calling 14bb into a 50.5bb pot needs 27.7% equity, and every part of a QQ+/AK range clears that. Facing the next raise is tighter: calling a 100bb 5-bet shove after a 21bb 4-bet costs 79bb into a 201.5bb pot, needing 39.2%. AKs has 41.9% against QQ+/AK and is a call; AKo has 38.8% and is a genuine coin-flip decision that should hinge on how often that player 5-bet bluffs.

What is a 5-bet in poker?

The raise over a 4-bet — the fifth bet of the sequence. At 100bb stacks it is almost always all-in, because a 4-bet has already put roughly a fifth of the stack in and there is no room for a meaningful non-committing raise. A 5-bet range is therefore very narrow: the hands you are happy stacking off with, plus the occasional blocker-heavy bluff against an opponent whose 4-bet range is wide.