Overcards
An overcard is a card games on the flop that is higher than the highest card in your hand. It represent the threat that it has paired one of your opponent’s hole cards.
If you have T♣ T ♥ then you definitely would not like a flop like K ♥ 8 ♦ 6♠ against six players. Any player betting in front of you is representing at least a pair of Kings. Whether or not he actually has a King is for you to figure out and it usually means you’ll have to fold your hand, even if you sometimes actually have the best hand at that point.
You have to have an Ace in the pocket to not have to worry about an overcard, and that’s going to happen only 14.9% of the time. The X in the following table represents any card lower than the one named.
Percent Chance That You Will Flop an overcard 
You Hold 
None 
One 
Two 
Three 
One or More 
An overcard and No Set if paired 
K♣K♦OR KX 
77.449 
21.222 
1.408 
0.020 
22.550 
11.67 
Q♦Q♥OR QX 
58.571 
35.143 
6.000 
0.286 
41.429 
31.12 
J♥ J♠ OR JX 
43.041 
43.041 
12.796 
1.122 
56.959 
46.96 
T♠T♣ OR TX 
30.531 
45.796 
20.816 
2.875 
69.487 
59.57 
9♣ 9♦ OR 9X 
20.714 
44.388 
29.082 
5.816 
79.286 
69.30 
8♦ 8♥ OR 8X 
13.265 
39.796 
36.612 
10.327 
86.735 
76.54 
7♥ 7♠ OR 7X 
7.857 
33.000 
42.429 
16.714 
92.143 
81.65 
6♠ 6♣ OR 6X 
4.163 
24.980 
36.612 
25.306 
95.837 
85.01 
5♣ 5♦ OR 5X 
1.857 
16.714 
45.551 
36.429 
98.143 
86.97 
4♦ 4♥ OR 4X 
0.612 
9.184 
39.796 
50.408 
99.3898 
87.92 
3♥ 3♠ OR 3X 
0.102 
3.367 
28.959 
67.571 
99.898 
88.22 
2♠ 2♣ 
impossible 
0.245 
11.510 
88.245 
1000.00 

None, one, two and three means the chance of having exactly that many overcards come on the flop. For example, if you hold Q ♥ Q♣, there will be exactly two overcards (Aces or Kings) on the flop 6.0% of the time. The One or More column is simply the total of the one, two and three columns. Hold'em no limit .
Note that there is barely any difference between a pair of deuces and a pair of eights in the pocket when it comes to flopping an overcard. A Jack in the pocket is the median hand for flopping an overcard. A Jack in the pocket is the median hand for flopping an overcard. You’ll get one or more 57% of the time while you’ll flop an overcard to a Queen only 41% of the time. That is why in a multiway pot I do not raising preflop with J ♥ J ♦ in the pocket. I know I’ll get an overcard over half the time so I see the flop as cheaply as possible.
The column on the far right gives the odds of getting at least one overcard and not flopping a set when you hold a pair in the pocket. In other words, it gives the odds that you won’t like the flop 