The switch decision is complicated. Most of the time it will be obvious. The following tables can be used to determine whether or not to switch in any situation under the usual rules. The player hand is along the left column and the dealer's up card is along the top row. To use the table add the expected values by switching and not switching and play the pair of hands with the greater expected value. An example follows the table. Also note there is a different value for a blackjack according to whether it was natural or the result of a switch. Most casinos treat a blackjack after switching as 21 points, thus pushing to a dealer 21 or 22.
Switching StrategyExpand
Player
2
3
4
5
6
7
8
9
10
A
5
-0.2695
-0.1883
-0.1509
-0.1121
-0.0723
-0.1566
-0.2219
-0.2979
-0.3448
-0.3484
6
-0.2832
-0.2004
-0.1626
-0.1236
-0.0823
-0.1891
-0.2520
-0.3250
-0.3696
-0.3732
7
-0.2551
-0.1721
-0.1347
-0.0954
-0.0561
-0.1166
-0.2558
-0.3266
-0.3607
-0.3908
8
-0.1694
-0.0884
-0.0528
-0.0172
0.0178
0.0347
-0.1049
-0.2526
-0.2918
-0.3059
9
-0.0721
0.0075
0.0384
0.0715
0.1334
0.1245
0.0534
-0.0956
-0.1957
-0.1669
10
0.0593
0.2213
0.2792
0.3386
0.3940
0.2704
0.1697
0.0722
-0.0185
-0.0088
11
0.1728
0.3313
0.3851
0.4401
0.4926
0.3362
0.2296
0.1150
0.0734
0.0639
12
-0.3561
-0.3005
-0.2783
-0.2538
-0.2108
-0.2482
-0.3055
-0.3722
-0.4086
-0.4128
13
-0.4026
-0.3439
-0.2989
-0.2551
-0.2110
-0.3021
-0.3553
-0.4130
-0.4507
-0.4544
14
-0.4389
-0.3436
-0.2993
-0.2553
-0.2110
-0.3526
-0.3977
-0.4552
-0.4901
-0.4933
15
-0.4382
-0.3436
-0.2993
-0.2556
-0.2117
-0.3946
-0.4406
-0.4943
-0.5267
-0.5297
16
-0.4385
-0.3442
-0.2998
-0.2561
-0.2131
-0.4348
-0.4774
-0.5272
-0.5575
-0.5605
17
-0.3081
-0.2175
-0.1767
-0.1382
-0.0984
-0.1731
-0.4444
-0.4789
-0.4751
-0.5677
18
-0.0416
0.0406
0.0709
0.1022
0.1315
0.3343
0.0442
-0.2419
-0.2324
-0.2772
19
0.2264
0.2986
0.3187
0.3439
0.3618
0.5510
0.5318
0.2277
0.0103
0.1376
20
0.4829
0.5466
0.5594
0.5752
0.5873
0.7077
0.7307
0.7001
0.5009
0.5472
A,2
-0.0895
-0.0208
0.0105
0.0432
0.0766
0.0754
0.0106
-0.0749
-0.1428
-0.1378
A,3
-0.1226
-0.0444
-0.0118
0.0216
0.0564
0.0338
-0.0248
-0.1098
-0.1761
-0.1713
A,4
-0.1462
-0.0659
-0.0336
0.0006
0.0365
-0.0054
-0.0665
-0.1478
-0.2102
-0.2061
A,5
-0.1673
-0.0863
-0.0531
-0.0185
0.0217
-0.0470
-0.1061
-0.1849
-0.2453
-0.2412
A,6
-0.1471
-0.0658
-0.0327
0.0068
0.0745
0.0037
-0.1189
-0.1911
-0.2399
-0.2628
A,7
-0.0401
0.0439
0.0752
0.1168
0.1779
0.3364
0.0473
-0.1433
-0.1884
-0.2023
A,8
0.2272
0.3020
0.3222
0.3463
0.3634
0.5518
0.5353
0.2311
0.0049
0.1355
A,9
0.4837
0.5492
0.5609
0.5767
0.5884
0.7090
0.7310
0.7025
0.4974
0.5510
BJ (switched)
0.7282
0.7866
0.7921
0.7980
0.8032
0.8613
0.8703
0.8829
0.9060
0.8505
BJ (natural)
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
A,A
0.1795
0.3383
0.3923
0.4474
0.5018
0.3487
0.2428
0.1265
0.0717
0.0155
2,2
-0.2548
-0.1748
-0.1389
-0.0831
0.0147
-0.1101
-0.1933
-0.2720
-0.3204
-0.3247
3,3
-0.2833
-0.2013
-0.1622
-0.1101
-0.0103
-0.1661
-0.2520
-0.3249
-0.3696
-0.3733
4,4
-0.1692
-0.0884
-0.0522
-0.0160
0.0196
0.0359
-0.1041
-0.2525
-0.2912
-0.3049
5,5
0.0603
0.2224
0.2808
0.3429
0.4005
0.2739
0.1705
0.0719
-0.0186
-0.0086
6,6
-0.3571
-0.3004
-0.2599
-0.1645
-0.0624
-0.2517
-0.3083
-0.3741
-0.4106
-0.4142
7,7
-0.4369
-0.2850
-0.1968
-0.1061
-0.0102
-0.1829
-0.4016
-0.4600
-0.4962
-0.4984
8,8
-0.2984
-0.0946
-0.0146
0.0627
0.1461
0.1814
-0.1555
-0.5026
-0.5576
-0.5595
9,9
-0.0401
0.0417
0.0988
0.1730
0.2442
0.3359
0.1220
-0.1844
-0.2297
-0.2738
10,10
0.4829
0.5466
0.5594
0.5752
0.5873
0.7077
0.7307
0.7001
0.5009
0.5472
Example:Hand 1 is Q7, hand 2 is 9J, and the dealer is showing a 2. The player can not switch and have a 17 and 19, or switch and have a 20 and 16. The value of a 17 and 19 is -0.3081+.2264 = -0.0817. The value of a 20 and 16 is 0.4829-.4385=+0.0444. So, in this case, the 20 and 16 is better, so the player should switch.
The switching strategy based on the Las Vegas rules table is only wrong in548 cases out 100,000, the probability of a mistake is 0.37% and these mistakeswould increase the house edge by a negligible 0.0002%. There are about 300differences between the switching strategies for Playtech and Las Vegas rules,most of them when the dealer is showing a 6, 10, or an ace, but none when thedealer is showing an 8.
Strategy Calculator
My Blackjack Switch calculator, courtesy of Jing Ding, will advise when to switch in any situation. The calculator is based on the Playtech rules and an infinite deck assumption.
