Blackjack side bets: why their house edge is higher
A side bet pays a fixed multiple on a rare event, and the pay table sits below the fair odds. Because the event is rare, a small shortfall in the payout is a large share of each stake. Side bets are settled apart from the hand, so good play cannot lower their cost.
What a side bet is
A side bet is an extra stake placed next to the main hand. It is settled on its own rule, usually something that happens in the first cards, such as a pair or cards of the same suit. The guide to the blackjack house edge covers the main hand; this guide covers why the extras are priced differently.
The cost of any bet comes from two numbers: the probability of the event and the multiple paid when it happens. The same formula applies to every bet in this guide, and the expected value entry explains it in general terms.
The formula for any pay table
Suppose a bet wins with probability p and pays n to 1. A stake of one unit then returns n units of profit with probability p, and loses one unit with probability 1 minus p.
expected value = (p × n) − (1 − p) = p × (n + 1) − 1
The house edge is the negative of this value. The fair payout, where the edge is zero, is n = (1 − p) / p. Any payout below that figure gives the house an edge, and the pay table is where that choice is made.
A fully worked side bet
The real side bets on offer differ from game to game, and their pay tables are the operator's choice. To keep every step checkable, this guide builds a simple one from scratch.
The bet: "the first card dealt to the player is an ace", from a single deck of 52 cards with 4 aces. The probability is 4/52 = 1/13. Suppose the pay table gives 10 to 1.
(1/13 × 10) − (12/13 × 1) = 10/13 − 12/13 = −2/13 ≈ −15.38%
The fair payout is (12/13) / (1/13) = 12 to 1. The pay table is 2 units short of that, and 2 units out of every 13 staked is the edge. A stake of KES 100 loses KES 15.38 on average each round.
The same ace bet works for a shoe of several decks. With 8 decks there are 32 aces in 416 cards, and 32/416 = 1/13 again, so this particular bet does not depend on the number of decks.
How the pay table sets the edge
Changing only the multiple, with the event unchanged, moves the edge in a straight line. Each unit removed from the payout adds 1/13, about 7.69 percentage points, to the cost of the ace bet.
| Payout (ace as first card, 1/13) | Average result per unit staked | House edge |
|---|---|---|
| 8 to 1 | 8/13 − 12/13 = −4/13 | about 30.77% |
| 10 to 1 | 10/13 − 12/13 = −2/13 | about 15.38% |
| 11 to 1 | 11/13 − 12/13 = −1/13 | about 7.69% |
| 12 to 1 | 12/13 − 12/13 = 0 | 0% |
Two tables can offer the same side bet with different pay tables. The names and the cards are identical, and the cost per stake differs by several percentage points.
Why rarer events cost more
A second illustration makes the event rarer: "the first two cards are both aces", again from a single deck.
The probability is 4/52 × 3/51 = 12/2652 = 1/221. The fair payout is 220 to 1. Suppose the pay table gives 100 to 1.
(1/221 × 100) − (220/221 × 1) = 100/221 − 220/221 = −120/221 ≈ −54.30%
A payout of 200 to 1 would still fall short: (200 − 220)/221 = −20/221, an edge of about 9.05%.
The pattern is that the fair payout grows as the event gets rarer, and a table that rounds the payout down loses a larger share of the stake each time. A headline multiple of 100 to 1 looks generous, yet the example above costs more than half of every stake on average.
The main hand compared
On the main hand, the event "player wins" has a probability near but below one half, and a win pays 1 to 1. The fair payout for a bet that wins with probability near 0.5 is close to 1 to 1, so a payout of exactly 1 to 1 leaves only a small gap. That is why the main hand edge is small, as in the guide to RTP and house edge.
A side bet turns the same kind of shortfall into a large share of the stake. Each example above is a few units short of the fair payout, and because the win happens once in 13 or once in 221 rounds, each unit short is a visible fraction of what is staked.
Side bets are independent of the hand
A side bet is settled on cards dealt, before the player chooses to hit, stand, double or split. Nothing done on the hand can change the probability that the first card is an ace. Good play lowers the cost of the main hand only.
A round has KES 100 on the main hand and KES 20 on the ace bet at 10 to 1. If the main hand had an edge of 1% (an assumed figure for this example only), its average cost is KES 1.00. The ace bet costs 20 × 2/13 ≈ KES 3.08. The side bet is one sixth of the KES 120 staked and about three quarters of the total average cost (3.08 out of 4.08).
Adding side bets blends their price into the whole session. The share of money placed on them matters more than the size of the main bet.
Frequency and swings
A bet that pays 10 to 1 once in 13 rounds has long gaps with no payout. Over 100 rounds the ace bet is expected to hit about 7.7 times (100/13), but 3 hits or 13 hits are both ordinary. The volatility entry explains why these swings do not change the average cost, only how far a session can sit from it.
Where to find the actual figures
This guide uses invented pay tables and does not state the edge of any real side bet. Real figures depend on the pay table and the number of decks, so they belong to the game rules shown on screen. In Kenya, regulation 20(2) of the Gambling Control (Conduct of Gambling Operations) Regulations, 2026 requires a licensee to "display clearly rules of games, odds, house edge and average return to the player". Regulation 23(1) requires a licensee to "clearly display betting odds, rules and terms applicable to each bet", and regulation 45(1) requires online game rules to be displayed before any wager.
A reader can check a displayed figure with the formula above: take the payout for each outcome, the probability of each outcome, and add up the products. The same sum also applies to a bet such as the baccarat tie bet. Gambling is addictive; play responsibly, and see the responsible gambling page for limits and the GRA helpline. This content is for adults aged 18+.
Questions and answers
Why is the house edge on side bets higher than on the main blackjack hand?
The main hand pays close to even money on an outcome that happens close to half the time, so small rule differences leave a small edge. A side bet pays a large multiple on a rare event, and the gap between the payout and the fair odds is a large share of the stake. Worked example: a bet on an ace as the first card from one deck, paid 10 to 1, costs 2/13 of each stake, about 15.38%.
Can basic strategy lower the house edge on a side bet?
No. Basic strategy is a set of decisions about the hand: hit, stand, double or split. A side bet is settled on the first cards or a fixed event, before any of those decisions, so no decision on the hand changes its probability or its payout.
What does a pay table do to the edge?
The pay table lists the multiple paid for each outcome. Raising one payout lowers the edge and lowering it raises the edge. In the worked one-deck ace bet, a payout of 12 to 1 would be fair, 11 to 1 costs about 7.69% and 8 to 1 costs about 30.77%.
Does the number of decks change a side bet?
It can. A bet on the first card depends only on how many aces are in the pack as a share of all cards, which is the same for one deck or eight. A bet on two cards matching, such as two aces, depends on the cards left after the first is dealt, so the probability changes slightly with the number of decks.
Where should the edge of a side bet be found?
In the rules displayed for the game. Regulation 20(2) of the 2026 Conduct of Gambling Operations Regulations requires a licensee to display clearly the rules of games, odds, house edge and average return to the player, and regulation 45(1) requires online rules to be displayed before any wager.