55 vs A4s: preflop equity

The exact count puts 55 at 66.31% and A4s at 33.69% when the two hands see all five board cards.

55

66.31%

Wins 66.05%, ties 0.53%

A4s

33.69%

Wins 33.42%, ties 0.53%

Equity counts a tie as half a win. Exact over every board.

55 against A4s: the numbers

Exact preflop results for 55 against A4s, in percent
HandWinsTiesLosesEquity
5566.0490.53033.42166.314
A4s33.4210.53066.04933.686

55, a pocket pair, plays A4s, a suited hand. One of the other hand's cards outranks the pair and one is below it, which makes this a closer race than a pair against two small cards.

55 is well ahead, and A4s needs a specific kind of board to catch up. Of every 100 boards, about 0.53 are split pots, and the equity figures already include them.

55 ranks number 27 of 169 starting hands, and A4s ranks number 35, by equity against a random hand.

Boards behind the percentages: 41,095,296 counted in all
HandBoards won, aboutBoards tied, aboutBoards lost, about
5527,143,000218,00013,734,000
A4s13,734,000218,00027,143,000

The total is exact: 24 specific deals times 1,712,304 boards. The three counts are approximate, worked out from the percentages to five decimals and rounded to the nearest thousand.

55 against A4s read as odds
HandEquity as odds (to 1)Wins one deal inLoses one deal inPot odds needed to call (to 1)
551.9691.5142.9920.508
A4s0.5082.9921.5141.969

The last column is the smallest pot odds, written as a pot-to-call ratio, at which a call breaks even with this equity.

Who is ahead on which flops

Across the five flop textures 55's equity moves by 18.08 points, from 62.62% on monotone flops to 80.70% on low rainbow flops (nine high or lower). 55 stays ahead on all five textures, but the swing between them is large, so how the flop looks matters a great deal.

55 against A4s by flop texture, in percent
FlopShare of flops55 winsTiesA4s wins55 equity
Rainbow, ten or higher25.22065.9640.29133.74566.110
Rainbow, nine or lower5.68980.2740.85318.87380.701
Two-tone46.54565.3350.36134.30465.516
Monotone5.21261.3022.63536.06362.619
Paired17.33464.8470.59234.56165.143

Read the flop types this way: rainbow has three suits, two-tone has two cards of one suit, monotone has three, and paired repeats a rank.

Compared with a random hand

Each hand has a baseline against a random hand: 60.33% for 55, 59.03% for A4s. Here the change is +5.98 and -25.34 points.

55 and A4s here compared with each against a random hand, in percent
CaseEquity hereAgainst a random handChange in pointsTimes the random-hand equity
55, all flops66.31460.325+5.9891.09928
55, rainbow, ten or higher66.11060.325+5.7851.09590
55, rainbow, nine or lower80.70160.325+20.3761.33777
55, two-tone65.51660.325+5.1911.08605
55, monotone62.61960.325+2.2941.03803
55, paired65.14360.325+4.8181.07987
A4s, all flops33.68659.034-25.3480.57062
A4s, rainbow, ten or higher33.89059.034-25.1440.57408
A4s, rainbow, nine or lower19.29959.034-39.7350.32691
A4s, two-tone34.48459.034-24.5500.58414
A4s, monotone37.38159.034-21.6530.63321
A4s, paired34.85759.034-24.1770.59046

Does a shared suit matter?

The suit split reads 66.58% for 55 with a shared suit and 66.05% without one. 55 does better with a shared suit, by 0.53 points.

55 against A4s by suit overlap, in percent
DealsSpecific dealsShare of deals55 winsTiesA4s wins55 equity
Share a suit1250.0066.2910.57033.13966.576
No shared suit1250.0065.8060.49033.70466.051

How often this matchup comes up

The class pair covers 24 combinations of specific cards in a fixed seat order, 0.0015% of 1,624,350, and 48 (0.0030%) in either order.

A worked example

Put $100 each into a $200 pot and deal every board once: 55 averages $132.62 back, ahead of its $100 by $32.62, while A4s averages $67.38, short of its $100 by $32.62.

Per 1,000 deals: 55 wins about 661, A4s wins about 334, and about 5 end in a split pot.

The same matchup from the other side

A4s versus 55 is this same page seen from the other hand: 33.69% for A4s, 66.31% for 55.

Try 5s5h against Ad4d in the calculator: the hands share no suit, and every card can be changed. The links after it are the closest matchups in the ranking.

How this was computed

Nothing here is simulated. The 24 deals of 55 against A4s fall into a few suit patterns, each dealt against all 1,712,304 boards, with both best five-card hands compared on every board. Ties give each hand half a win, and the flop rows count a board under each of its ten flops.

Source: our own exact count from the GeorgeLiPoker poker math library. No outside data is used.

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