About accuracy

PlayCorrect’s tables come from an expected-value engine, not from copying a published chart. We then check the results. This page is the public summary of that work. It is educational, for adults 21 and over, and is not a claim that using the site will overcome the house edge.

Method, in brief

The engine values each legal action from a finite shoe with the current player cards and dealer upcard removed. The dealer’s finish is a memoized distribution over 17–21 and bust. The player’s hit decisions do not “see” the hole card; draw probabilities mix over legal holes under a US peek. Doubling draws one card and stands. Non-ace splits use an independence approximation for later hands, with a solved hand-count cap up to four hands; split aces are valued exactly and sequentially (no resplit, one card each). The published chart action is the frequency-weighted best play across two-card compositions of each total. Full notes live with the engine (METHOD.md in the project).

What we did not do: we did not import a lookup table, and we did not use a package that merely reprints Wizard of Odds charts.

Sources checked

• Wizard of Odds strategy calculator, last updated 3 Aug 2026 on the page we used, at wizardofodds.com/games/blackjack/strategy/calculator/. Compared cell by cell (350 cells: hard 5–21, soft 13–20, all pairs).
• Wizard of Odds 4–8 deck text chart, last updated 7 Nov 2026, used in the earlier primary-table check.
• Beating Bonuses strategy calculator for the primary six-deck S17 DAS, no-surrender table only (house edge printed 0.46% on the generated page).
• Wizard of Odds hand calculator for exact-card expected values.

We cite those sites as independent checks, not as something we copied wording or charts from.

Total-dependent charts — last checked 10 Nov 2026

Earlier the same day we had already matched six rule sets 350/350 (six-deck S17 DAS with and without late surrender, six-deck H17 DAS, and S17 DAS on 1, 2, and 8 decks), plus a 30-cell written spot-check and a 350/350 match against Beating Bonuses on the primary table. In the afternoon we compared all 32 chip-row tables to the Wizard of Odds calculator (six- and eight-deck tables against the “4 or more decks” setting).

• 29 of 32 rule sets matched 350/350 on that engine comparison.
• The 29 include every six- and eight-deck combination, every two-deck combination except one, and every one-deck combination except two closely related H17 DAS mixes.
• Three tables disagreed in a single close pair cell, all involving our split approximation:
  • 1-deck H17 DAS, 9,9 vs ace: our engine preferred stand (−0.18613) over split (−0.18765). Wizard of Odds prints split.
  • The same cell with late surrender: our engine still preferred stand; surrender is −0.500.
  • 2-deck H17 DAS with late surrender, 8,8 vs ace: our engine preferred split (−0.49611) over surrender (−0.50000). Wizard of Odds prints surrender-else-split.

On 10 Nov 2026 at 1:06 PM PT, Jake asked that those three cells follow the Wizard of Odds published play rather than more engine work on split EV. The calculator now plays split on the two one-deck 9,9 vs ace cells, and surrender-else-split on the two-deck 8,8 vs ace late-surrender cell, and labels the hand “Play follows Wizard of Odds on this close split cell.” A residual split-EV gap versus the Wizard of Odds hand calculator on 8,8 vs 9 was already noted in the Milestone 2 log (our split −0.388528 vs −0.390279; stand, hit, and double on that hand had matched). We did not invent new split numbers to close that gap.

Exact-card checks — last checked 10 Nov 2026

We originally verified ten default-rule exceptions, including 10,2 vs 4 and 4,5,7 vs 10, with EVs agreeing to six decimals. We then verified 21 more hands on the Wizard of Odds hand calculator (more six-deck 16s vs 10, two soft 18s vs ace, a five-card 16, and one- and two-deck two-card exceptions). All 21 matched on best play, and expected values agreed to the reported six decimals. Combined: 31 of 31 exact-card spot-checks matched. Other exceptions remain labeled computed.

What “verified” on a badge means

A rule-mix badge of “chart-verified” means the 350-cell total-dependent grid matched Wizard of Odds on 10 Nov 2026. An exact-card note marked verified means that specific holding was checked on the hand calculator. Computed means the engine produced the number and we have not yet spot-checked that holding. The full log is in the project’s accuracy-report.md and engine/verification.md.

None of this is a promise about future sessions at a table. 21+. Study here; do not use a phone at the casino table.