Calculating poker odds can be easy for some games and difficult for others. The key to calculating poker odds properly is having a solid understanding of the math behind the poker game you are playing. In 7 Card Stud HL for example. If the other player has 4 low cards on the board, it is safe to assume that he will qualify for the low hand. If you do not have a better possible low hand or at least a high pair, you should fold.
2-7 Triple Draw is another game that requires the use of an odds calculator. There really isn’t a reliable odds calc out there for 27 Triple Draw though. You will have to calculate the odds, including the pot odds, in your head.
If he draws 1 card on the last draw and you do the same, you might want to call his final bet even if you caught a high card. The odds of him pairing up or catching a higher cards as well as the pot odds, will indicate that calling is +EV in most cases.