Enter the pot and the bet you are facing. Get the pot odds, the equity you need to call, and a plain-English read on whether to do it.
You need about 25% equity to break even on the call. For one card, a flush draw is about 18%, an open-ender 16%, and a gutshot 8%. The familiar 36% / 32% / 16% figures apply only when you are guaranteed both cards.
Pot means the chips in the middle before your opponent bets. The formula is equity needed = call ÷ (pot before the bet + bet + call).
Say the pot is $100 before your opponent bets $50. Calling $50 creates a $200 pot, so you need 50 ÷ 200 = 25% equity. In ratio terms that is 3-to-1: the pot pays three chips for every one you risk.
Count the cards that make your hand. Against an ordinary one-street bet, use outs × 2 for the next card. Use outs × 4 against the current price only when the call closes the action and guarantees both remaining cards. Otherwise any next-card shortfall needs realistic implied odds.
Start with the pot before the bet. Divide the call by pot + bet + call. If the pot is $100 and your opponent bets $50, calling $50 creates $200 total: 50 ÷ 200 = 25%.
Good pot odds are ones your hand can beat on the relevant street. At 3-to-1 you need 25%; a flush draw is only about 18% for the next card, so a normal flop call needs implied odds. If the call is all-in and guarantees both cards, its roughly 35% by-river chance clears the price.
Pot odds are the price the pot offers you. Equity is how often your hand wins. You call when your equity is higher than the equity the pot odds demand, and fold when it is lower.