G-Bucks is a concept coined by poker pro Phil Galfond that helps you to calculate the expected value of a hand against a range of hands. It is basically an extension of Sklansky Dollars, which calculates the expected value of your hand against one particular hand. The similarity between the concepts is that they both give you an idea of how much money you could have won or lost when you take your equity and set it against a certain situation.
Understanding G-Bucks begins with understanding Sklansky Dollars....
As I mentioned, G-Bucks are an extension of Sklansky Dollars, a theory created by American poker theorist and professional David Sklansky. Sklansky Dollars are imaginary and don't have any actual value themselves, but the concept allows you to see how much money you can expect to win in the long run if you play a certain hand against another certain hand. The operative words here are in the long run. After all, even a hand that will win most of the time won't win all the time. Read up on Sklansky Dollars to get the full picture.
G-Bucks adopts this theory and then takes it a step further to account for hand range. Now you can see how much equity you have based on a more comprehensive spectrum of possible hands. We don't actually know exactly what cards are opponents are holding, but if we've been paying attention, we can determine the range of hands our opponents tend to play in certain situations - and this knowledge can pay off, big time.
The reverse also holds true...
Galfond actually calculates G-Bucks by using your perceived range and the opponent's actual hand. While both will work, realistically, we never actually know our opponent's exact holdings, so I like to calculate G Bucks using my hand and my opponent's range.
How to Calculate G-Bucks
Not only will G-Bucks make you a lot of money by helping you wisely and lucratively pick and choose your battles, but it's also appealingly simple to calculate.
First, pin your opponent down to a range. (Read up on how to determine and balance ranges).
Next, figure out your equity. You can do this by entering your hand and your opponent's range into any poker calculator. You can also do it yourself, and while I think it is good to know how to do this calculation, it is generally faster to just use a calculator.
Finally, you're going to multiply your percentage of equity in the hand by the pot size and presto - you can see how much you'll win in the long run.
G-Bucks in Action
Hold ‘on to your butts, ‘cause things are about to get real. You may have to read this a couple times (or a few) to get a solid handle on the nuances, but it WILL come. It’s like learning to ride a bike: once you got it, you got it.
Let’s get into it then.
Say you've got K♦Q♦, you raised to $3 before the flop and your opponent re-raised you out of position to $10 (which you deem to signify a reasonably strong holding). You called since KQ suited can do a lot on the right flops.
You think that your opponent would re-raise you with the following hands:
AK , AQ , AA , KK , QQ , JJ , TT  and 99 .
*The numbers in the square bracket refer to the combinations of each hand (see article on combinatorics) and determines the weighting and likelihood of him holding each hand. This is important because our G-bucks are based on our chances of winning against the entire range of hands, and our calculation result would be pretty meaningless if we counted his AK hands as often as his pocket aces.
Against this range of hands, our equity is about 33%, so our G-bucks in the hand would be $6 ($20 pot X 33% equity).
The flop comes down J♦, T♦ and 7♠, giving us an open-ended straight flush draw. Our opponent bets out $15 into the $20 pot, which we will expect him to do with all the hands he re-raised with pre-flop. We call.
Our G-bucks are now equal to $26 ($50 pot x 52% equity). If we folded to the bet, we would surrender the pot and lose $0 further. But by investing the $15 we expect to win $26 on average for a net gain of $11, making this a winning call.
The turn is a 2♣, and our opponent bets half the pot: $25. At this point we think he will be checking his AKs and AQs (unless he has a flush draw, but since we have both the King and Queen of diamonds, he cannot have a flush draw) and betting all his pocket pairs.
His range now looks like this: AA , KK , QQ , JJ , TT , 99 .
*The combinations of JJ and TT dropped from 6 to 3, because of card removal.
Against this range, our equity is 35%.
Therefore, when our opponent bets $25 into $50, we should call. If we fold, we lose $0, but if we call we are looking at winning 35% of (25+25+50 = 100) for $35, which is greater than the cost of a $25 call.
If our opponent bet $100 into $50, on the other hand, we would want to fold since the amount of G-bucks we expect to win would be less than the amount of real money we had to put in to continue.
G bucks = 35% (50+100+100) = $87.5
Cost of Call = $100
Net Gain from Call = -$12.5
This is why bet size is so important!
Your decision to continue is based on your opponents bet size as well as their range; this is how you seek out profitable investment decisions in poker.
If, however, we thought our opponent would keep betting with ALL hands, and his range looked the same as it did on the flop, then our equity would be 33%, which would slightly change things, but not by too much.
G-Bucks on the River
This is the end of G-bucks as they pertain to equity, but there are also G-bucks which relate to pot odds on the river. Remember: when you make a river call you don't need to show a winner every time to make a long-run profit. You just need to be winning the pot often enough to match the odds the pot is laying you.
So, the river is K♥...
A question for you: you've made top pair of kings and you now beat the QQ and 99 hands in your opponents range, but lose to the AA, KK, JJ and TT hands. Assuming your opponent keeps betting no matter what his hand is, what bet size can you call and still be making money?
Hint: Based on card removal, your opponents range looks like this: AA  KK  QQ  JJ  TT  99 .
Spoiler: Combos that beat our pair of kings: 13 (AA,KK, JJ, TT). Combos that are bluffing against our pair of kings: 9 (QQ,99).
Total combos: 22, ~60% are value bets, ~40% are bluffs (relative to our pair or kings).
If our opponent bets 2x the pot, we will be getting 3:2 odds on our call ($200 to win $500; original $100 pot + his $200 + our $200 back). If we think he is bluffing, 40% of the time we can call a bet double the size of the pot.
This may be extremely shocking - that we could call even an overbet here - but consider this: when our opponent bets 1/2 the pot, he only has to be bluffing 25% of the time for us to have a profitable call. When he bets the full pot, it becomes 33% of the time.
The fact that he has such a high amount of bluffs compared to value bets (hands that beat us) means we can call a very big bet. In fact, if you are in a spot where you think half of the hands your opponent is betting are bluffs, you can call a bet of any size, no matter how big it is relative to the pot.
Bonus: Assuming your opponent bets the same hands but checks when he has pocket queens, how does this change things?
Spoiler: Combos that beat our pair of kings: 13 (AA,KK,JJ,TT). Combos that are bluffing against our pair of kings: 6 (99).
Total combos: 19, ~69% are value bets, ~31% are bluffs.
Now, if our opponent bets the full pot or $100 we must fold. Any amount less than this we can profitably call.
Bonus Question #2: Assuming your opponent checks both his QQ and 99 hands, what bet size can you call?
Answer: No bet size. If he checks with QQ and 99, he is only betting with hands that beat our pair of kings and we are burning every penny that we place into the pot in this situation.
Mind spinning a bit? That’s OK! G-Bucks is a pretty advanced topic, but once you master it, it’s a concept that will optimize your edge. The good news is you don’t have to lock yourself in your room, forsaking friends and family forever to do all the math yourself. I offer a nifty, FREE equity calculator that will let you see how often hands beat each other or beat ranges.
Now, you are going to have to embrace SOME math to really optimize your edge, but this tool will help, and it can be used in combination with the math to break down hands, equity and then G-bucks, which as you may recall, is equity vs. range * amount in pot.
Now get out there, be fruitful and multiply your winnings!