# 40bb 3-bet all-in from the small blind: chipEV vs ICM ranges

Source: https://poker.academy/blog/post/40bb-is-it-too-big-to-3bet-all-in
Author: Filip Pedzich
Published: 2024-07-17 · Updated: 2026-09-17
Category: Theory

![40bb 3-bet all-in from the small blind: chipEV vs ICM ranges](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-hero.jpg)

40 big blinds feels like a lot of room. You can open, 3-bet small, flat and still play poker after the flop. So moving all-in with 40bb over a single open sounds reckless. The solver disagrees, a little. It does jam 40bb from the small blind, with a thin slice of hands, and which slice depends on who opened and on how the tournament pays.

I pulled the spots straight from the Poker Academy preflop solutions. **ChipEV:** CE-Symmetric, 9-handed MTT, everyone 40bb, 1bb big-blind ante, 2.3bb opens. **ICM:** three 9-handed 40bb sims with a classic ante (0.12bb per player, 1.08bb in total) and 2.25bb opens, at 100, 50 and 20 players left. Percentages are shares of all 1,326 starting hands unless I say otherwise.

## The maths of a 40bb jam

The CO opens to 2.3bb and the button folds. The pot is 2.3 + 0.5 + 1 + 1 = 4.8bb. If you jam from the small blind, you put in 39.5bb more to win those 4.8bb when everyone folds.

A jam with no equity when called

fold needed=39.539.5+4.8=39.544.3=89.2%\text{fold needed} = \frac{39.5}{39.5 + 4.8} = \frac{39.5}{44.3} = 89.2\%

In the chipEV sim the big blind folds 93.4% of hands to that jam and the CO folds 78.3% of its opening range. Together that’s 0.934 × 0.783 = 73.1% (ignoring card removal), well short of 89.2%. So a 40bb jam is never a pure bluff. It needs hands that do fine when they get called, and it has to take equity away from hands that would otherwise see a flop.

## SB vs CO: 1.8% jams

Against a CO open the small blind folds 72.6%, calls 14.4%, 3-bets to 8bb with 11.3% and jams 1.8% of hands. The jam is not the top of the range: AA, KK and QQ 3-bet small.

![Poker Academy preflop chart, 40bb CE-Symmetric chipEV 9-handed, SB vs 2.3bb CO open: fold 72.6%, call 14.4%, raise 8bb 11.3%, all-in 1.8%](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-ce-sb-vs-co-fig.jpg)

*40bb chipEV, SB vs a CO open. Dark red = all-in 40bb, orange = 3-bet to 8bb, teal = call.*

The hands that jam, with their all-in frequency:

- Always: JTs (100%).
- Most of the time: AQo (71%).
- Part of the time: 88 (44%), KTs (42%), KJs (32%).
- A little: QJs 14%, AJo 13%, KQo 12%, QTs 11%, AKo 8%, 99 6%.

My reading, as a heuristic: these hands have decent equity against a calling range but are awkward after a small 3-bet, facing a 4-bet shove or a big pot out of position. JTs is the only pure jam here.

## How the CO answers the jam

The CO is getting a price: 37.7bb to call into a 44.3bb pot.

CO calls the 40bb jam

37.737.7+44.3=37.782=46.0%\frac{37.7}{37.7 + 44.3} = \frac{37.7}{82} = 46.0\%

It still folds most of its opening range. The CO opens 36.8% of hands at 40bb and calls the jam with 21.7% of that range: AA–77 (66 half the time), AKs–ATs, AKo, AQo, KQs, KJs, AJo about half the time and KTs a little. Everything else folds. The app shows it on the node itself, including the pot odds.

![Poker Academy preflop chart, 40bb chipEV, CO facing a small blind 3-bet all-in: fold 78.3%, call 21.7% of its opening range](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-ce-co-vs-jam-fig.jpg)

*40bb chipEV, CO opened 2.3bb and faces a 40bb SB jam. Teal = call, grey = fold, hatched = not in the CO’s opening range.*

[pa-cta id=”open_mtt_40bb_sb_vs_btn” to=”/open/mtt-40bb-sb-vs-btn” title=”SB facing a button open, 40bb, chipEV” body=”The chipEV half of the comparison: the same node the ICM link prices differently.” label=”Open the matrix”]

## SB vs BTN: 4.1% jams

Against a button open the small blind jams more than twice as often: 4.1% of hands, with 13.0% 3-bets to 8bb, 11.6% calls and 71.4% folds.

![Poker Academy preflop chart, 40bb chipEV, SB vs 2.3bb BTN open: fold 71.4%, call 11.6%, raise 8bb 13.0%, all-in 4.1%](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-ce-sb-vs-btn-fig.jpg)

*40bb chipEV, SB vs a BTN open.*

- Always: AQo, QTs, JTs (100%), 77 (96%).
- Most of the time: KTs, AJo (74%), KQo (55%), 88 (52%).
- Part of the time: 44 (42%), A5s (35%), 55 and QJs (24%).

The opener is what widens it, not the stack: that is 40bb in both spots. The button opens 50.6% of hands and the CO 36.8%, so the button’s range is wider and weaker. It folds a similar share of it to the jam (79.0% against 78.3%) and calls with 21.0% of it. My reading: the button’s calls come out of a weaker opening range, so more medium pairs and broadways have enough to jam.

## What ICM does to the same spot

ChipEV counts chips. ICM counts prize money, and in a tournament the chips you lose are worth more than the chips you win. The ICM sims here use a 30-place payout: 1st gets 19.2% of the prize pool, 2nd 13.8%, 3rd 10.38%, down to 1.85% for 10th to 13th and 1.12% for 24th to 30th. Each has the whole table at 40bb; the rest of the field has other stacks, and the average across all players left is 35bb. The app labels them by field size left: 50% (100 players, 70 from the money), 25% (50 players, 20 from the money) and 10% (20 players, already in the money).

![Chart: small blind strategy at 40bb against CO and BTN opens in chipEV and in ICM with 100, 50 and 20 players left](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-sb-mix.png)

*Share of all 1,326 hands. The ICM sims open 2.25bb and use a classic ante, so the comparison is close but not identical.*

| 40bb SB, all-in / 3-bet small / call / fold | vs CO open | vs BTN open |
| --- | --- | --- |
| ChipEV | 1.8 / 11.3 / 14.4 / 72.6 | 4.1 / 13.0 / 11.6 / 71.4 |
| ICM, 100 left | 0.2 / 11.0 / 13.6 / 75.3 | 1.2 / 12.9 / 15.2 / 70.7 |
| ICM, 50 left | 1.3 / 10.0 / 9.1 / 79.5 | 3.0 / 12.2 / 9.6 / 75.2 |
| ICM, 20 left | – / 9.5 / 14.0 / 76.5 | – / 11.6 / 17.2 / 71.1 |

Percent of all hands. A dash means the tree has no all-in option in that sim.

In both ICM sims that offer the jam it comes out smaller than in chipEV, and it doesn’t shrink in a straight line: with 50 left it’s bigger than with 100 left.

## 20 left: the chipEV jams become calls

In the money, with 20 players left, the solution has no small blind all-in at all. One honest note: this sim’s tree only gives the small blind fold, call and a 3-bet to 7.6bb, so the solver never tested the jam and turned it down. What you can read from it is what happens to the hands that jammed in chipEV:

![Poker Academy preflop chart, 40bb ICM 10% field left, SB vs 2.25bb CO open: fold 76.5%, call 14.0%, raise 7.6bb 9.5%](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-icm20-sb-vs-co-fig.jpg)

*40bb ICM, 20 players left (in the money), SB vs a CO open. No all-in option in this tree.*

- JTs, KJs and KTs call 100%.
- 88 calls 93% and 3-bets 7%.
- AQo calls 75% and 3-bets 25%.

Against the button it’s the same picture: JTs, QTs, KTs, 88, 77 and 44 call every time, while AQo, AJo and KQo split between a call and a 3-bet to 7.6bb. An earlier version of this post said the all-ins “switch to almost pure calls”. For the CO spot that holds, in the same sim. It just wasn’t the solver turning the jam down.

## 50 left: the callers tighten more than the jammer

With 50 players left, 20 from the money, the jam is back: 1.3% against the CO and 3.0% against the button. That’s more than at 100 left. The reason sits on the other side of the table.

![Poker Academy preflop chart, 40bb ICM 25% field left, CO facing a 40bb SB jam: fold 87.0%, call 13.0% of its opening range](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-icm50-co-vs-jam-fig.jpg)

*40bb ICM, 50 players left, CO opened 2.25bb and faces the SB jam: call 13.0% of the opening range.*

Near the bubble the CO calls the jam with only 13.0% of its opening range, against 21.7% in chipEV: AA–TT, AKs, AQs, AKo and AQo most of the time. The big blind folds 96.2%. With both players folding, the jam wins the pot right away 83.7% of the time, against 73.1% in chipEV.

![Chart: how often a 40bb small blind jam wins the pot uncontested in chipEV and ICM with 100 and 50 players left](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-folds.png)

*Big blind fold share × opener fold share of its opening range, from the solver’s response nodes. Card removal ignored.*

In ICM the small blind loses more prize equity when it gets called, but it gets called much less. Against the button that trade is good enough for a clear jam range:

![Poker Academy preflop chart, 40bb ICM 25% field left, SB vs 2.25bb BTN open: fold 75.2%, call 9.6%, raise 7.6bb 12.2%, all-in 3.0%](https://poker.academy/wp-media/2026/09/40bb-is-it-too-big-to-3bet-all-in-icm50-sb-vs-btn-fig.jpg)

*40bb ICM, 50 players left, SB vs a BTN open: all-in 3.0%.*

- Always: A4s, A2s, KJs, KTs, AQo (100%), A3s (95%), QJs (92%), A5s (86%).
- Mostly gone: the pairs (44 jams 14%). 77 and 88 now call, and JTs and QTs call too.

The jam range moves from pairs and connected broadways towards suited aces. My reading, as a heuristic: an ace blocks the calling range (AA, AK, AQ), and a hand like A4s still has some equity when it does get called. A small pair would rather see a cheap flop than put its tournament life on a flip.

With 100 left the jam is small: 0.2% against the CO (KJs 33%, AQo 10%) and 1.2% against the button (KJs 78%, KTs 67%, AQo 50%, QTs 47%). The CO calls 17.3% of its opening range there, so the fold equity sits between chipEV and the bubble.

[pa-cta id=”open_mtt_40bb_sb_vs_btn_icm” to=”/open/mtt-40bb-sb-vs-btn-icm” title=”SB facing a button open, 40bb, ICM” body=”The same node as the chipEV version, priced with 100 players left. This is the article’s thesis in one screen.” label=”Open the matrix”]

## So, is 40bb too big to 3-bet all-in?

- No, but it’s a small play. 1.8% of hands against a CO open and 4.1% against a button open in chipEV.
- It’s not your best hands. AA, KK and QQ 3-bet small. Jams are hands like JTs, AQo, KTs and medium pairs.
- The opener matters, the stack is the same. The button opens 50.6% and gets jammed more.
- ICM shrinks the jam at 100 and 50 left, and the 20-left sim doesn’t offer it at all.
- Near the bubble, watch the caller. When openers call a jam much tighter, the jam comes back with suited aces.

None of this is a rule to memorise hand by hand. The mix changes with the ante, the open size and the payouts, so look up the spot that matches your tournament.

[pa-cta id=”jam40_trainer” to=”/gto-trainer” title=”Practise the 40bb small blind” body=”Pick 40bb and the small blind vs RFI spots. The trainer deals the hands and grades each decision against the solver.” label=”Start training”]

Cheers! 🙂