Forty Thieves: 104 cards, one pass, and no single-deck version to lean on
Forty Thieves is a two-deck game by birth. Forty cards go face up into ten columns of four, the other 64 wait in a stock you turn once, and every build must follow suit, one card at a time. A second deck usually means more landing spots. Here it mostly means more cards to dig through with very little room to do it.
Our look-ahead program played 3,000 deals on this site's rules without seeing the stock and without Undo. It won 5.8% (174 of 3,000; 95% range 5.0%–6.7%) and brought home 34.3 of 104 cards on average (33.5–35.1). Compare two other 104-card games we measured with similar program types: Solitaire Double at 81.5% and Diplomat at 47.9%. Doubling the deck is not what makes a game easy; the rules around it decide that.
At a glance: Forty Thieves among the two-deck games
| 104-card game (program type) | Won | 95% range | Deals |
|---|---|---|---|
| Forty Thieves (look-ahead, stock unknown) | 5.8% | 5.0%–6.7% | 3,000 |
| Diplomat (look-ahead, stock unknown) | 47.9% | 45.7%–50.0% | 2,000 |
| Solitaire Double (priority-list program) | 81.5% | 80.7%–82.2% | 10,000 |
| FreeCell Two Decks (solver, all cards visible) | 88.0% solved | 84.4%–90.8% | 400 |
The programs differ, so this is a rough map, not a ranking. Two more Forty Thieves figures: its wins took 277.3 moves including stock turns (273.0–281.7, 174 wins), and 57.3% of deals had an Ace playable from the opening tableau (55.5%–59.1%). There is no one-deck Forty Thieves on the site and no published figure (Blake and Gent 2026 do not cover it), so we cannot say what the second deck changes within this game itself.
Rules on this site
- Cards: two decks, 104 cards.
- Tableau: ten columns of four, face up.
- Stock: 64 cards, turned one at a time to a waste pile; the top waste card plays.
- Redeals: none.
- Foundations: eight, two per suit, Ace to King.
- Building: down in the same suit, one card at a time.
- Empty columns: any card.
Why two decks feel so tight here
Twins do not help same-suit building much
In Solitaire Double a red 6 has four possible black 7s. In Forty Thieves the 6 of hearts has exactly two 7s of hearts, and one may be under three other cards. The second deck adds copies, but the suit rule keeps the choice narrow.
A long stock with no second pass
Sixty-four cards go through once. Every card you cannot use stacks on the waste and hides the one below. Turn only when the table is ready to catch what comes.
Space is the scarce resource
There are no free cells. An empty column is the only extra room, and single-card moves mean it is worth a lot. Clear the easiest column first and guard it.
Use both foundations of a suit
With two piles per suit, a card has two ways home. Keep both piles moving so neither copy of a needed card is stranded.
Undo is your window into the stock
Our program never saw a stock card before turning it. You can turn, look, and undo if the timing was wrong.
Common two-deck traps
- Chasing the twin you cannot reach while the other copy is free on the waste.
- Turning stock cards to "see" with nowhere to put them.
- Filling a gap with a lone card that could have waited.
- Forgetting there is no second pass.
Forty Thieves on freecell-two-decks.com
Free in any modern browser on computer, tablet or phone, with no account. Unlimited Undo, Hint, Restart and Auto Play are there, plus zoom and fullscreen for ten columns, drag or tap to move, a count of wins, time and moves, and sound and table color settings.
How we measured it
The freecell-two-decks.com team ran this test in September 2026 on this site's own Forty Thieves rules.
- Rules from the site code: ten columns of four, 64-card single-pass stock, same-suit building, single-card moves, any card in a space.
- 3,000 numbered deals, seeds 1–3,000.
- A look-ahead program that weighs up to 300 positions per move using visible cards only, turns the stock when nothing improves, and never undoes.
- No greedy baseline, no solver and no published figure, so 5.8% is a weak floor, not a winnable share. The solitairex.io site puts Forty Thieves in a tier at 11% or less, with no method given.
- Comparison games used their own programs; see each game's page.
- Ranges: Wilson score for percentages, normal intervals for averages.
Python 3.11, standard library only. Claude, an AI assistant by Anthropic, helped write and review the code and draft this page; every figure comes from running the code.
Forty Thieves questions
Is 5.8% my chance of winning?
No. It is a weak program with no Undo. Patient players do better.
Why is it so much harder than Solitaire Double?
Same-suit building, single-card moves and one pass through the stock. The deck size is the same; the room is not.
What should I play next?
FreeCell Two Decks gives 104 cards with eight free cells and nothing hidden. Diplomat is a gentler one-pass game. The full list is on the games page.
By Admin, freecell-two-decks.com (Forty Media). Research run September 2026.