When deciding whether to call a bet in poker, you should use pot odds to help with your decision. Pot Odds is the ratio of the current size of the pot to the call you need to make. For instance, if the pot contains $30 and you need to make a call of $10 to stay in the hand, the pot odds are $30 to $10 or 3:1. To convert this to a percentage, you add the size of the pot part of the ratio (3) to the call part of the ratio (1) to get 4. To get the percentage you divide the sum 4 by 1 which is 25% (1/4).

If you are drawing for instance, ie: you have 4 cards to a flush with cards to come, you can use the pot odds in comparison to the liklihood of drawing a card to a winning hand to determine your move.

Using the example above your pot odds will be 3-to-1, or 25 percent. If you are on a flush draw you have a 4.3-1 odds against hitting the flush with one card to go. (there are 9 cards that help you out of 46 remaining cards, approximately 19 percent or 4.3-to-1 odds against). In that case, the pot is not offering adequate pot odds for the call unless you thinks you can induce additional betting from your opponent if you hit the flush draw.

Download this handy Pot Odds Chart for reference