Forty Thieves Solitaire: two packs, one pass, and every move counting
Forty Thieves is a two-pack game with a reputation for being hard, and the rules explain why. You build only in suit, you move one card at a time, and you get one trip through the stock with no second chance. Forty cards start face up on the table, which is where the name is usually said to come from.
We measured it with a computer player that sees only what you see and never undoes a move. It won 5.8% of 3,000 deals. That is a floor, not the true odds: our player is weak at this game, and a patient person with Undo will do better. But it shows how much careful play Forty Thieves demands.
What a Forty Thieves deal gives you
| What we measured | Result | Deals | How |
|---|---|---|---|
| An Ace is playable from the opening tableau | 57.3% (95% range 55.5–59.1%) | 3,000 | Deal inspection |
| Computer player's win rate | 5.8% (5.0–6.7%) | 3,000 | Look-ahead player, doesn't know the stock, no Undo: a weak floor |
| Cards home at the end of a game (of 104) | 34.3 on average | 3,000 | Same player, all games |
| Moves in a won game (including stock turns) | about 277 | 174 wins | Same player |
We found no published figure for Forty Thieves to compare against.
Forty Thieves rules on klondike.nz
The layout
- Two standard packs shuffled together: 104 cards.
- Ten tableau columns of four cards each, all face up (40 cards).
- The other 64 cards form the stock.
- Eight foundations, two per suit, built up from Ace to King.
Moves
- A card may go on the next higher card of the same suit.
- Only one card moves at a time; you cannot move a run in one step.
- Any card may go into an empty column.
- The stock turns one card at a time onto the waste, and the top waste card can be played.
- There is no redeal: once the stock is used up, it is gone.
- You win when all 104 cards are home.
Reading the deal
An Ace is waiting in a bit over half of deals
In 57.3% of our deals, at least one of the eight Aces was at the bottom of a column and could go straight home. In the rest, your first Aces will come from digging or from the stock.
Spot the same-suit neighbours
Because building is by suit, the first thing to spot is where a card could go on its same-suit neighbour: a 6 of clubs on a 7 of clubs. Those are your moves; alternating colours count for nothing here.
Find the column you can empty
Every column starts with only four cards. Look for one whose cards can all go elsewhere, onto foundations or same-suit neighbours. An empty column takes any card, and in a one-card-at-a-time game it is the most useful space on the table.
Remember the stock is a single pass
Sixty-four cards will come out of the stock once each. Anything you can't use when it appears either goes onto the waste pile, where only the top card is playable, or is lost for good under later cards.
Strategy
Work the tableau before turning the stock
Every stock card you turn and can't use buries the one before it. Before you click, make every tableau move that helps.
Don't clog the waste
Your waste pile grows throughout the game, and only its top card is free. Try to play waste cards as they appear, and avoid turning the stock when you have no plan for what might come.
Prize empty columns
With single-card moves, an empty column is how you rearrange a stack: park a card, move the next, bring the first back. Spend them carefully.
Keep track of both copies
There are two of every card. If one 8 of spades is buried, check whether the other is easier to reach before committing to a long dig.
Accept that some deals get away
Even played well, Forty Thieves is unforgiving. Our player got on average just 34 of the 104 cards home. Undo is there to explore different orders, and a new deal is always one click away.
A worked opening
Suppose the deal shows an Ace of hearts at the bottom of one column and a 2 of hearts at the bottom of another. Send both home at once. If that empties a column, don't rush to fill it: first check whether any four-card column could be cleared into it card by card, because two empty columns together are worth far more than one. Only then start on the stock, playing each card as it appears if it goes home or onto its same-suit neighbour.
Similar games
For the same two-pack scale with a more forgiving stock, try Solitaire Double. Diplomat uses two packs and a single pass too, but builds in any suit. For an in-suit game with every card face up, try Eight Off.
Playing Forty Thieves on klondike.nz
Free, with nothing to download or sign up for, in any modern browser on a computer, tablet or phone. With 104 cards, zoom and fullscreen mode are useful; you can tap a card and its destination instead of dragging. Hint, unlimited Undo, Restart and Auto Play are all there, and the game tracks wins, time and moves.
Where these numbers come from
The klondike.nz team measured Forty Thieves in September 2026 using this site's own rules.
- Rules from our code. The game's Forty Thieves settings: two packs, ten columns of four face up, a 64-card stock turned one at a time with no redeal, in-suit building, one card per move, any card into an empty column.
- A program copy of the game. We adapted the program we built for Diplomat, another two-pack game, to these rules.
- Numbered deals. 3,000 deals from numbered seeds, repeatable exactly.
- Reading each deal. We checked whether an Ace could be played from the opening tableau.
- The player. It looks ahead up to 300 positions each turn using the cards it can see, doesn't know the stock order, and never undoes a move.
- Comparison. We found no published figure for this game.
- Error bars. The 95% range for the player's win rate is 5.0–6.7%.
- Limits. This player is weak at Forty Thieves. Its 5.8% says how hard the game is to win without looking far ahead or undoing moves; it is not how many deals can be won, and we have no solver result for that.
Under the bonnet
The code is Python 3.11 with only the standard library, in the module fortythieves.py. Each turn the player runs a small best-first search of up to 300 positions over the moves it can see, remembering positions it has already considered, and then plays the best first step. Deals are run in parallel over processor cores with multiprocessing, and ranges are Wilson score 95% intervals. An AI assistant, Claude by Anthropic, helped write and review the code and draft this page. The figures come from running the code, not from the AI.
Questions players ask
Where does the name come from?
The usual explanation is the forty cards dealt face up at the start, though the origin of the name isn't well documented.
Is there a second pass through the stock?
No. Forty Thieves here has no redeal.
How do I shift a whole stack?
No, one card at a time. Use empty columns to move a stack in stages.
How winnable is Forty Thieves?
We can only give a floor: our computer player won 5.8%. Careful players with Undo will do better, but we haven't measured how many deals are winnable with perfect play.
Who ran this study?
The klondike.nz team; see our about page.
By Admin, klondike.nz. Study date: 19 September 2026.