// ICM calculator · 4 left · 3 paid

SNG bubble: the chip leader shoves on the second stack

Seat 1 shoves and Seat 2 has to decide. In chips the call needs 47.9% equity; under ICM it needs 71.6%, a risk premium of 23.6%.

Four left, three paid. The chip leader covers everyone and shoves into the second stack, who would be busting on the bubble with two shorter stacks still in. Losing costs a near-certain min-cash; winning only adds a little to a stack that was already safe, so the price of calling goes far beyond what the chips alone say.

SeatChipsShareP(1st)P(2nd)P(3rd)ICM valueChip-EV valueICM − chips
Seat 1shoves6,00044.4%44.4%31.2%18.0%35.1844.44-9.26
Seat 2calls?3,50025.9%25.9%29.9%27.7%27.4625.93+1.53
Seat 32,50018.5%18.5%23.6%30.8%22.5018.52+3.98
Seat 41,50011.1%11.1%15.3%23.6%14.8611.11+3.75

Seat 2 facing Seat 1’s shove

Equity needed, ICM71.6%
Equity needed, chip EV47.9%
Risk premium+23.6%
Bubble factor2.73
If Seat 2…Seat 2 chipsSeat 1 chipsSeat 2 ICM valueChange vs folding
Fold3,5006,30027.27·
Call and win7,3002,50038.11+10.84
Call and losebusted9,8000.00-27.27

The working

  1. What is at risk. The smaller stack decides it: Seat 2 risks 3,500 chips to win 3,500 plus the 300 already in the middle.
  2. Chip EV. Calling breaks even in chips when equity × 7,300 = 3,500, so the call needs 3,500 ÷ 7,300 = 47.95%.
  3. ICM. Calling with equity q is worth q × 38.11 + (1 − q) × 0.00; folding is worth 27.27. They are equal at q = (27.27 − 0.00) ÷ (38.11 − 0.00) = 71.56%.
  4. Bubble factor. Prize equity lost per chip lost, over prize equity won per chip won: (27.27 ÷ 3,500) ÷ (10.84 ÷ 3,800) = 2.73. Above one, a chip lost costs more than a chip won is worth.
  5. What chip EV gets wrong. A call with exactly the chip-EV break-even equity, 47.95%, is free in chips but costs 9.00 in prize equity against folding.

Which hands can call

Against a shover holding the top 20% of hands (40 hand classes, 276 combos, ranked as on /hands), each starting hand’s all-in equity compared with the two prices above.

Shover’s range, top
calls under ICM calls at chip EV only (equity shown) folds either way

ICM calls with 2 hand classes (0.9% of hands). Chip EV would call with 19 (9.5%). Folds under ICM that chip EV calls: QQ, JJ, TT, 99, 88, AKs, 77, AQs, AJs, AKo, ATs, AQo and 5 more.

The working, for Seat 2

  1. First place. The model gives each player the tournament with probability equal to their share of the chips: 3,500 ÷ 13,500 = 25.93%.
  2. Second place. Someone else wins, then Seat 2 takes first among the players left, again in proportion to chips. Summed over who won: (6,000/13,500)·(3,500/7,500) + (2,500/13,500)·(3,500/11,000) + (1,500/13,500)·(3,500/12,000) = 29.87%.
  3. Every later place works the same way, over every order in which the places above can be filled. That is 4! = 24 finishing orders in all, summed exactly (no sampling).
  4. ICM value. Each place's probability times its prize: 25.93% × 50.00 + 29.87% × 30.00 + 27.65% × 20.00 = 27.46. If prizes were paid in proportion to chips the same stack would be worth 25.93.
// settle the thread

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// what is computed, and what is assumed
  • Computed exactly: every seat’s probability of every place, summed over every finishing order, then each prize times its probability. No sampling.
  • Assumed: the Independent Chip Model. Your chance of finishing first is your share of the chips, and each later place goes the same way among the players left (Malmuth-Harville). It knows nothing about skill, position, the size of the blinds, or who is about to be in the big blind. Where the model is wrong, so are these numbers, and it is a model, not a solve.
  • Assumed: the hand ends the decision. The call price compares this hand only: fold now, or get the chips in and see a showdown. It does not value the spots a bigger stack will get later, which is what future-game simulations try to add.
  • Splits count as half a win, as equity always does. Under ICM a split pot leaves stacks almost unchanged, which is worth very nearly the same.
  • Which hands call uses the engine’s preflop all-in equity matrix (200,000 sampled run-outs per hand pair, card removal applied), so a hand within a few tenths of a point of the price could fall either side. The shove range is the top X% by equity against a random hand: an assumption about the shover, not a read. For shove and call ranges that are solved rather than assumed, at equal stacks, see the ICM push/fold charts.
  • Input: stacks in chips, and the prizes still to be decided, largest first, in any unit: percent, dollars, or seats. Prizes already banked do not change any decision, so leave them out. The pot is any chips already in the middle (blinds and antes), not counted in anyone’s stack.

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