Casino games are games of chance with a built-in house edge. No strategy, system or choice of timing changes the odds in the player’s favor over time, and most players lose money over the long run. Nobody should gamble money they cannot afford to lose. This article explains why one particular kind of wager tends to be more expensive than the rest, not how to get an advantage from it, because there is none.
What a side bet is
Many table games offer a main wager and, next to it, one or more optional extras. In blackjack the extra might pay if your first two cards form a certain pattern, or if the dealer’s up card is a certain rank. In some poker-style table games an extra wager pays on the strength of your hand regardless of what the dealer holds. In dice games, a group of one-roll wagers sits in the middle of the layout. What they share is that they are separate from the core game: you can play without them, they are resolved on their own rule, and they come with their own payout table.
Because each is an independent bet, each has its own house edge. The main game’s edge says nothing about the extra bet’s edge. This is the root of most confusion about them.
The basic arithmetic
The house edge of any bet is the expected loss divided by the amount wagered. Expected value, the probability-weighted average of all outcomes, is what makes this calculation work. A bet that pays at fair odds has an expected value of zero; a bet that pays less than fair odds has a negative one.
Here is a hypothetical side bet, invented only for illustration. Suppose it wins with probability 1 in 20 and pays 15 to 1. Over 20 equally likely outcomes, you would win 15 units once and lose 1 unit 19 times:
- Gains: 15
- Losses: 19
- Net: 15 minus 19 equals minus 4 units over 20 bets
That is an expected loss of 0.2 units per unit wagered, a 20 percent house edge. Fair odds for a 1-in-20 event would be 19 to 1, so the shortfall between 15 and 19 is the house’s cut.
A real, textbook example comes from dice. In craps, the wager that the next roll will total seven wins on 6 of the 36 equally likely outcomes of two dice. Fair odds are therefore 30 losing outcomes to 6 winning ones, or 5 to 1. When it pays 4 to 1, the expected value per unit is (4 × 6 − 30) / 36, which is minus 6/36, about 16.7 percent. Compare that with a single-number bet on a single-zero roulette wheel, which wins on 1 of 37 pockets and pays 35 to 1. Its expected value is (35 − 36) / 37, about minus 2.7 percent. Both are bets on a single narrow outcome, yet the cost differs by a wide margin because of the payout chosen. The detail of one-roll wagers belongs to the discussion of proposition bets, which have their own article.
Why the edges tend to be larger
There is no law that a side bet must cost more, but several features of how they are built push in that direction.
They are bets on rare events. A rare event with a large headline payout is attractive to look at. A payout of 25 to 1 sounds exciting even when the true odds are 40 to 1. People are generally poor at judging small probabilities, so the shortfall is hard to see.
The payout table can be tuned freely. The main game’s rules are tightly constrained by tradition and by regulation. A side bet is a newly designed product, so its designers can decide how many tiers of payouts it has and what each one pays. A game math model for a side bet is often built to hit a target margin first, and then the payout tiers are set to fit.
Low hit frequency. Side bets often have a low hit frequency, meaning most bets lose. That makes the swings in a session larger than the average suggests. An occasional large win can hide the steady drip of small losses, which is part of why the bet feels less costly than it is.
They add to the amount at risk. Even if a side bet had the same edge as the main game, adding it would increase the total wagered. With a higher edge, it raises expected loss much faster than its size suggests.
A combined example
Take a hypothetical round in which a player stakes 10 units on a main wager with a 1 percent edge, and 5 units on a side bet with a 10 percent edge. The expected loss on the main bet is 0.10 units. On the side bet it is 0.50 units. The total is 0.60 units on 15 units wagered, so the blended edge is 4 percent.
Notice that the side bet is one third of the money wagered but accounts for more than four fifths of the expected loss (0.50 of 0.60). Small add-ons can dominate the cost of a session. This effect is also why the figure that operators watch, the hold percentage, can look quite different between tables with and without such bets.
Variance and the “close to winning” feeling
Many side bets have high variance. Most of the time they lose; occasionally they pay a large multiple. Standard deviation per bet is large relative to the stake, so a short run of results tells you little about the true price. Over small samples, a side bet can look generous or stingy purely by chance, which is why a handful of lucky hits is not evidence that a bet is fair.
Near-hit outcomes can also feel meaningful. A hand that almost forms a qualifying pattern is still a loss, and the odds on the next round are unchanged. Past outcomes do not alter the odds of independent future events.
How to read an unfamiliar side bet
Without recommending anything, here is how a curious reader can assess whether a side bet is priced steeply:
- List every outcome that pays, with its probability. Published rules or independent math references normally give these.
- Multiply each payout by its probability, add them up, and subtract the probability of losing times the stake.
- Compare the result with the main game’s edge.
If the probabilities are not available, that is itself a sign that you cannot judge the price. Remember too that payout notation can mislead, since “30 for 1” returns less than “30 to 1”. Payout ratios are written in several ways, which is covered in its own article.
Keeping it in perspective
Skipping optional extras reduces the average cost of play without changing anything else about the game, but it does not make the game profitable. The house edge on the main wager remains. Anyone who plays should decide on a gambling budget in advance, treat it as the price of entertainment, and stop when it is gone. If gambling is causing worry or harm, support services in your area can offer confidential help.