Pokemon pull rate odds calculator
Pull rates confuse everyone because "1 in 100 packs" does not mean 100 packs guarantees one. Opening follows the coin-flip math of independent events, and this calculator does it properly.
Published pull rates are community estimates and vary by set and era; check a current source for your set. The math here is exact for whatever rate you enter. Expected value of opening vs holding sealed is a different question; see the booster pack guide.