This is one of the hands where many players hesitate. A total of 10 is good, but the dealer is showing a 9, which feels threatening. The instinct is to just hit and keep your options open. But basic strategy says to double, and the math confirms it.
Your odds of improving
With a total of 10, any card from ace through 10 gives you a playable hand. Drawing a 10-value card (about 30.8% of the deck) gives you 20. Drawing an ace gives you 21. Drawing a 9 gives you 19. In total, roughly 70% of cards give you 17 or better. Only drawing a 2 through 7 leaves you potentially behind.
What the dealer faces
The dealer showing 9 will make a pat hand (17-21) about 77% of the time. That sounds tough, but the dealer is not guaranteed a strong total. The bust rate for a dealer 9 is about 23%. And even when the dealer makes a hand, your doubled 10 will beat it often enough.
The expected value comparison
When you double 10 against dealer 9, your expected value is roughly +0.18 per unit bet. When you just hit, the expected value is about +0.15. Doubling adds more profit per hand played. Over hundreds of hands, that difference compounds. You are not just making the right play - you are making the most profitable play.
