Percent chance of no overcard, flop:

• K,K – 77%

• Q,Q – 59%

• J,J – 43%

• T,T – 31%

• 9,9 – 21%

• 8,8 – 13%

• 7,7 – 08%

• 6,6 – 04%

[Ed. note: In other words, chance of holding top-set or an overpair, after flop.
Never hurts to keep these numbers in mind]