
While it may be clear that you are in a good position to bet or raise, if you are unaware of how much you should be betting, you are handing an advantage to your opponents. If you bet too little, you are offering opponents who could possibly make a straight or a flush (known as drawing hands) a cheap opportunity to see another card which could then beat your hand. On the flip side, you could also bet too much on a hand which may already be beaten and lose more than was necessary. Understanding bet sizing allows you to make advantageous decisions and make the most of your opponents mistakes.
In order to size bets correctly, the size of your bet should always be in relation to the size of the pot.
This means that whenever you make a decision to bet or raise, you must work out how much to bet according to the value of the pot. For instance, if you feel you have the best hand and would like to make a bet when the pot is $20, you should be looking to bet 75%-100% of the value of the pot or $15-$20. In doing so, you will most likely remove players holding weak hands and offer the incorrect pot odds for players holding drawing hands to continue. If another player does have a better hand, you have not committed too much to the pot and will not have cost yourself more than necessary.
As a general rule, pre-flop raises should be around 3 or 4 times the big blind if there has not been any action before you. If players in an earlier position to you have called the Big Blind (limped in), you should add an extra Big Blind to your raise for every additional player. Again, this is to give your opponents worse odds in continuing the hand, as for every player who limps in, the value of the pot is increased thus you’re your raise needs to increase to prevent offering more favourable odds for your opponents to call.