How to Defend the Big Blind: The Price You Get, by Open Size
Your big blind defend range depends on two things: the open size, which sets your price, and the opener's seat, which sets the range you are up against. Against a 2.5x open with no ante the big blind needs 27.3% equity to call, against a min-raise 22.2% and against 3x 30.8%: the best price at the table, because its blind is already in the pot and, once the small blind folds, nobody can raise behind it. This site's range library defends 19.5% of hands against an under-the-gun open and 44.5% against a button open. And yes, the big blind can raise before the flop: a 3-bet against an open, or a raise with its option when everyone just calls.
The price, by open size
Say the button opens to x big blinds and the small blind folds. The pot holds the open, the small blind's 0.5bb and your 1bb, and calling costs x - 1 more, so the equity you need is what you put in over the pot you play for: (x - 1) / (2x + 0.5). Against a 2.5x open you call 1.5bb to play for a 5.5bb pot: 27.3%. The blind you already posted is money in the pot, which is why the big blind can call wider than any other seat. It is the same arithmetic as any pot odds call: in the pot odds calculator, put 2.5 in "Pot before the bet" (both blinds and the part of the open that matches yours) and x - 1 in "Bet to call".
| Open | Big blind | Big blind, 1bb ante | Small blind |
|---|---|---|---|
| 2x | 22.2% | 18.2% | 30.0% |
| 2.2x | 24.5% | 20.3% | 31.5% |
| 2.5x | 27.3% | 23.1% | 33.3% |
| 3x | 30.8% | 26.7% | 35.7% |
| 3.5x | 33.3% | 29.4% | 37.5% |
| 4x | 35.3% | 31.6% | 38.9% |
Big blind: the small blind has folded. Big blind, 1bb ante: the big-blind ante many tournaments now use, posted by the big blind for the whole table. Small blind: the same open, priced as if the big blind folds behind. It cannot count on that: the big blind can still raise, which makes the small blind's call worth less than this price suggests.
Why folding too much loses
Turn the price round and it is the opener's sum. A button open risks the raise to win the 1.5 big blinds already in, so as a pure bluff it breaks even when both blinds fold raise / (raise + 1.5) of the time. Fold more often than that between you, and the button makes money raising any two cards, from your folds alone. What is left over is the blinds' minimum defence frequency: how often at least one of you has to continue.
| Open | Steal must work | Blinds must continue |
|---|---|---|
| 2x | 57.1% | 42.9% |
| 2.2x | 59.5% | 40.5% |
| 2.5x | 62.5% | 37.5% |
| 3x | 66.7% | 33.3% |
| 3.5x | 70.0% | 30.0% |
| 4x | 72.7% | 27.3% |
If both blinds play this site's ranges, a button open gets two folds 44.7% of the time, counting every way the two blinds' hands can be dealt. That is short of the 62.5% a 2.5x steal needs from folds alone, so the button's open has to make its money with its cards when called, not with your folds. Defend much tighter and the folds alone pay for every open.
How wide to defend, by opener
The price depends on the size of the open, not on who made it. What changes with the seat is the range you are up against: in this site's range library, under the gun opens 9.8% of hands and the button 40.0%, so the same price buys a call with more hands against the button. (The positions lesson covers why late seats open wider.) The library's defend ranges, by opener:
| Spot | Opener's range | Defend | Combos |
|---|---|---|---|
| Big blind vs UTG | 9.8% | 19.5% | 258 |
| Big blind vs MP | 13.1% | 24.3% | 322 |
| Big blind vs cutoff | 23.1% | 32.7% | 434 |
| Big blind vs button | 40.0% | 44.5% | 590 |
| Small blind vs cutoff | 23.1% | 12.2% | 162 |
| Small blind vs button | 40.0% | 18.9% | 250 |
Shares of the 1,326 starting hands, counted in combinations. The library is curated for 6-max at 100 big blinds rather than solved, and the big blind chart in the preflop charts is its defence against the button. The small blind defends far tighter: it pays more to call and still has the big blind behind it.
Range against range: the opener's edge shrinks
All in before the flop, each opening range is ahead of the big blind range that answers it, by less and less as the open widens: 56.17% against 43.83% under the gun, 51.26% against 48.74% on the button. The small blind defends so tightly that its range is the favourite against both openers it faces. These are all-in figures, not profit: the opener has position for the rest of the hand, so they say whose range is ahead now, not who wins the money once the betting starts.
| Spot | Opener | Defender |
|---|---|---|
| Big blind vs UTG | 56.17% | 43.83% |
| Big blind vs MP | 55.97% | 44.03% |
| Big blind vs cutoff | 53.35% | 46.65% |
| Big blind vs button | 51.26% | 48.74% |
| Small blind vs cutoff | 44.24% | 55.76% |
| Small blind vs button | 42.80% | 57.20% |
From the site's 169 by 169 matrix of every starting hand against every other, 60,000 seeded deals per pair, averaged over every pair of combos the two ranges can hold at once, so card removal counts. The standard error is about 0.01 of a point on these rows, and no more than about 0.12 on any single hand below. Load the button's open against the big blind's defence to run one yourself.
Pricing a marginal defend
Against the button's range, every one of the 169 starting hands has more all-in equity than the 27.3% a 2.5x open asks for; the weakest, 72o, has 29.4%. If the price were the whole story the big blind would defend every hand. The library defends 44.5%, and the gap is out-of-position play. Raw equity assumes you see all five board cards for nothing, and out of position you do not: the opener bets after you on every street, you fold some hands that would have won, and you win less with the rest. That is equity realisation, and it is why the bottom of a defence range needs a cushion well above the price. Against the button's open:
| Hand | Equity vs the button's open | In the defend range |
|---|---|---|
| A2o | 46.2% | Yes |
| K7o | 41.7% | Yes |
| 87s | 39.6% | 3-bet range only |
| J9o | 38.5% | Yes |
| Q8o | 38.4% | Yes |
| 64s | 37.0% | No |
| T8o | 36.5% | No |
| J4s | 36.3% | Yes |
The library is not solved for this spot and does not cut at an equity line: it takes the top of one ranking of the 169 hands, a points score that weighs high cards most. So its edge is rough. Its defend range holds J4s with 36.3% and leaves out 87s with 39.6%, which its separate 3-bet range against the button includes. Suited connectors flop straights, flushes and draws they can keep playing, so out of position they keep more of their raw equity than offsuit and gapped hands do: if you defend wider than the library, start with them.
Can the big blind raise before the flop?
Yes, in two ways. Facing an open, a raise is a 3-bet: the library's 3-bet range against a button open covers 8.3% of hands, from big pairs for value to suited wheel aces as bluffs, and the preflop raising lesson builds a first 3-bet range. When nobody raises (everyone limps, or the small blind just completes), the betting ends with the big blind, which has the option: check and see the flop for free, or raise. The small blind never has the option or the last word. Calling the same 2.5x open asks it for 33.3%, because it has only half a blind in, and the big blind still acts behind it, so many hands that are a call in the big blind are a 3-bet or a fold from the small blind.
Related tools
Frequently asked
Can the big blind raise preflop?
Yes. Facing an open, the big blind can fold, call or re-raise, which is a 3-bet. If nobody raised, it has the option: when the betting comes back round, it can check or raise, even after everyone else has only called.
Can the big blind check?
Yes, when nobody has raised. If every player before it has only called the big blind or folded, its blind already matches the bet, so it can check and see the flop for free. Facing a raise there is no check: it is fold, call or raise.
What should the big blind do when everyone limps?
Check the hands that play badly out of position and raise the strong ones. Seeing the flop is free, so never fold, and make the raise bigger than a normal open: every limper is still in, and you will be out of position against them on every street after the flop.
How wide should the big blind defend against a min-raise?
Wider than against any other size. A 2x open asks for 22.2% equity, against 27.3% for 2.5x and 30.8% for 3x, from the same opening range. The library keeps one defence range per opener whatever the size, so against a min-raise treat it as the least you play.
How should the big blind play against the small blind?
With position, for once: when the small blind raises, the big blind acts last on every street after the flop. The price is worse than against a button open of the same size, because no third player's blind is in the pot: a 3x raise asks for 33.3%, against 30.8% from the button. The library opens 29.7% of hands from the small blind and has no separate big blind range for the spot; position lets you realise more of your equity than in any other big blind spot, which offsets part of the worse price.
How do antes change big blind defence in tournaments?
They make defending cheaper and stealing cheaper. With a big blind ante (one extra big blind for the whole table, as many tournaments now play), a 2.5x open asks the big blind for 23.1% instead of 27.3%, and a 2.2x open 20.3%. A 2.2x steal then needs both blinds to fold only 46.8% of the time, against 59.5% with no ante, so expect wider opens and defend wider against them.
Terms used in this article
Keep reading
New to poker? Take the free Poker 101 course →