How Casino Game Odds Work: House Edge, Probability, and Payouts

What Is "how casino game odds work"?

Definition

Casino game odds describe how often each outcome happens, and how much that outcome pays when it hits.

Odds start as probability. The casino maps that probability to payouts using rules and a paytable. If payouts match true probability, the game breaks even. In real games, payouts sit below true probability. That gap creates the house edge.

Key terms you must know

• Probability. The chance an outcome occurs on one bet. Example, 1 in 38 on American roulette for a single number.
• Payout. What the game pays when you win. This can include profit only or profit plus your stake, depending on the game. Read the rules so you know which one applies. See How to Read Casino Game Rules and Paytables.
• Expected value (EV). Your average result per bet over the long run. EV includes wins and losses weighted by probability.
• Variance, volatility. How swingy results feel in the short run. High variance games pay less often and in bigger chunks. Low variance games pay more often in smaller chunks.

How probability turns into EV

EV comes from two inputs, probability and payout. You multiply each outcome’s net result by its probability, then add them up.

When the sum is negative, the game favors the house. The more negative it is, the faster your bankroll tends to drop.

Why you can win now and still lose later

Short sessions run on variance. You can hit a hot streak, land a big payout, or dodge long losing runs.

Long sessions move toward EV. The law of large numbers pulls results toward the game’s average. If the house edge is 2 percent, the longer you play, the more your results tend to reflect that cost.

RTP is the same idea shown from the casino side, average return back to players. Use it to compare games, especially slots. See RTP Explained: How to Use Return to Player to Choose Slots.

The Math Behind Casino Odds: Probability, Expected Value, and House Edge

Probability basics, single events and multiple outcomes

Probability is the chance of a result. You can write it as a fraction, a percent, or odds.

A single event has one result you care about. Example, a coin flip landing heads. The probability is 1/2 or 50 percent.

Most casino bets have multiple outcomes. You might win, lose, or push. Each outcome has its own probability, and the payout can differ for each one.

When you track long play, focus on the average result, not short streaks. If you need a quick reset on streak thinking, read The Gambler’s Fallacy Explained (With Simple Examples).

Expected value (EV), the number that matters

Expected value is your average profit or loss per bet over many bets. EV combines probability and payout.

Use this formula.

• EV = (Win probability x win amount) minus (Loss probability x loss amount)

Simple example. You bet $1 on a game with a 48 percent chance to win $1 profit, and a 52 percent chance to lose $1.

• EV = (0.48 x $1) minus (0.52 x $1) = minus $0.04

Your average loss is 4 cents per $1 bet. That is the cost of the game, before comps and promos.

House edge, what it means and how casinos calculate it

House edge is the casino’s average profit as a percent of your wager.

If a $1 bet has EV of minus $0.04, the house edge is 4 percent.

• House edge = (Expected loss per bet) divided by (Bet size)

House edge does not predict your next result. It describes the long-run average. Long sessions tend to move toward it.

For quick definitions across games, use the Casino Terminology Glossary: House Edge, RTP, Variance, and More.

RTP vs house edge, why both get used

RTP is the return to player. It shows the average percent paid back to players over time.

• RTP = 100 percent minus house edge
• House edge 4 percent equals RTP 96 percent

Table game players often talk in house edge. Slot players often see RTP on the paytable or game info screen. Both describe the same math from different sides.

Why rules and payouts change the edge

Odds change when the payout changes, or when the probabilities change. Small rule tweaks can shift EV fast.

• Blackjack: paying 6:5 instead of 3:2 lowers the win amount on blackjacks. EV drops, house edge rises.
• Roulette: adding a double-zero adds losing outcomes without raising payouts. EV drops, house edge rises.
• Video poker: changing one line in the paytable changes the average return. Two machines can look similar and have different RTP.

When you compare games, compare the exact rules and the exact payouts. That is where the edge lives.

How Payouts (Paytables) Convert Probability Into “Odds”

True odds vs casino odds

Probability tells you how often something should happen. The paytable tells you what the casino pays when it happens.

True odds use a fair payout. Casino odds use a slightly worse payout. That gap creates house edge.

Example, a 1-in-38 event has a true payout of 37 to 1 on a 1-unit bet. American roulette pays 35 to 1. You lose 2 units of value each time that win shows up, compared to fair odds.

Most casino games work the same way. The probabilities come from the rules. The paytable sets the price you get for those probabilities.

Implied probability from payout odds

You can convert any payout into an implied probability. Use this quick rule for “to 1” payouts.

• Implied probability = 1 / (payout + 1)

Example, a 35 to 1 payout implies 1/36 = 2.78%. On American roulette the true chance is 1/38 = 2.63%. The payout suggests a better chance than you actually have. That difference is house edge.

Common misunderstandings:

• Players treat payout odds as the true odds. They are not. They are the casino’s price.
• Players ignore the “+1” for getting your stake back. A 1 to 1 payoff implies a 50% break-even chance, not 100%.
• Players assume past results change the next result. They do not. Learn the basics at The Gambler’s Fallacy Explained (With Simple Examples).

Pushes, commissions, and side bets

Small rule details change EV fast because they change the effective payout.

• Pushes. A push returns your bet. It lowers risk, but it can also lower EV if the game uses pushes to reduce paid wins. Blackjack “push on 22” variants do this. Some baccarat side bets pay pushes as losses. Read the felt.
• Commissions. Baccarat banker often charges 5% commission on wins. That reduces your net payout. It can still be the best main bet because the win rate is high, but the commission is part of the math.
• Side bets. They often pay huge odds on rare events. The paytable usually lags the true odds by a lot. Treat side bets as entertainment unless you have the full table and can compute EV.

When you compare games, compare the full paytable, including fees and special rules. RTP summaries help, but the paytable tells you where the edge comes from. See RTP Explained: How to Use Return to Player to Choose Slots.

Variance and volatility, same edge, different ride

Two games can share the same house edge and feel nothing alike. Paytables shape variance.

• Frequent small wins. More hits, smaller payouts. You last longer on average, but you rarely spike a big profit.
• Rare big wins. Fewer hits, larger payouts. Your bankroll swings harder. You can bust faster, even at the same RTP.

Slots show this clearly. Two slots can both list 96% RTP, but one pays steady small wins while the other stores value in rare bonuses. If you play slots, use volatility as a selection tool. See Slot Volatility & Variance Explained: What It Means for Your Wins.

Odds by Game Type: Why Some Casino Games Are Better (or Worse) for Players

Blackjack: Rules, Strategy, and How Your Decisions Change EV

Blackjack gives you real control. Your choices change expected value.

With strong rules and perfect basic strategy, the house edge often sits around 0.3% to 0.8%. With weak rules or bad play, it can jump to 2% to 5%+.

• Play with a basic strategy chart. It removes most avoidable mistakes.
• Look for player-friendly rules. Dealer stands on soft 17, blackjack pays 3:2, double after split allowed, resplit options.
• Avoid side bets. Many run 5% to 15%+ house edge even when the main game is strong.

Roulette: European vs American vs Triple-Zero

Roulette is fixed-odds. You cannot outplay the wheel. The zeros set the edge.

• Choose European when you can. It cuts the edge about in half vs American.
• Avoid triple-zero. It is a large hidden cost for the same gameplay.
• Outside bets do not reduce the edge. Red, black, even, odd still carry the same house edge as most other bets on that wheel.

Craps: Pass Line vs Proposition Bets

Craps mixes low-edge core bets with high-edge propositions. The table layout makes it easy to overpay the house.

• Pass Line sits around 1.41% house edge.
• Don’t Pass sits around 1.36% house edge, but pushes on 12 in many casinos.
• Come and Don’t Come are close to the same edges as Pass and Don’t Pass.
• Odds bets have 0% house edge. They do not change the casino’s advantage on the base bet, but they reduce your total blended edge by adding fair money behind it.
• Proposition bets can be brutal. Many sit around 5% to 17%+ house edge, depending on the bet and pay table.

If you want better odds, keep your action on line bets and take odds. Limit the props.

Baccarat: Banker vs Player vs Tie

Baccarat has simple choices. The edges differ a lot.

• Banker is usually best, around 1.06% house edge with a typical 5% commission on Banker wins.
• Player sits around 1.24% house edge.
• Tie is the trap. It often runs around 14%+ house edge, depending on the payout.

If you want to keep the edge low, bet Banker or Player. Skip Tie and most side bets.

Slots: RTP Ranges, Hit Frequency, Volatility, and Bonus Features

Slots lock your odds into the math model. You cannot improve EV with skill.

RTP varies by game and jurisdiction. Many modern slots land around 88% to 97% RTP, with some higher in specific markets and some lower in regulated minimum-RTP areas.

• RTP tells you the long-run return. It does not tell you how smooth the ride feels.
• Hit frequency tells you how often you win something. It can still mean many small wins that return less than your bet.
• Volatility tells you how much value sits in rare events like bonuses, free spins, and multipliers.
• Bonus features change payout shape. Buy-bonus options and feature spins often increase swing and can carry different effective costs than base spins.

If you want a steadier session, pick lower volatility and higher hit frequency. If you chase big wins, expect deeper drawdowns and more losing streaks even at the same RTP. For RNG basics, see Casino RNG Explained: How Random Number Generators Work.

Video Poker: Paytables and Why Full Pay Matters

Video poker can offer some of the best odds in the casino, but only with the right paytable and correct play.

Small paytable changes create big EV changes. A “tight” table can add multiple percentage points of house edge.

• Full-pay games can push house edge near 0% with perfect strategy on certain variants.
• Short-pay games often sit around 1% to 4%+ house edge, even if you play well.
• Learn the correct holds. Strategy errors cost real money because the game is decision-driven.

Before you sit down, check the paytable. If you want definitions for RTP, house edge, and variance, use the Casino Terminology Glossary.

Online vs Land-Based Odds: RNGs, Game Rules, and What Actually Changes

Online and land-based casinos use the same math. Your results change when the rules change, not because the game sits on a screen.

• RNG vs physical gear: Online games use RNGs. Roulette wheels and card shoes use hardware. Both should produce random outcomes over time.
• Rule sets drive edge: Blackjack tables vary by dealer hits soft 17, double rules, and surrender. Roulette varies by single-zero vs double-zero. Baccarat stays tight on Banker, side bets do not.
• RTP and paytables: Online slots and video poker show RTP or reveal it through paytables. Land-based versions often post less detail. The paytable still controls your long-run return.
• Speed changes variance: Online play runs more hands and spins per hour. Your bankroll swings faster, even if the edge stays the same.

Read our detailed guide: Online vs Land-Based Odds: RNGs, Game Rules, and What Actually Changes - How Casino Game Odds Work: House Edge, Probability, and Payouts

Practical Ways to Use Odds Knowledge (Without Chasing Systems)

Pick Lower-Edge Games, Then Avoid the High-Edge Bets

Your main lever is game selection. House edge sets your long-run cost per dollar wagered. Start with lower-edge games. Then remove the worst bet options inside them.

Ignore hot and cold streak talk. It pushes you toward worse bets and bigger swings. If you want a clean explanation of why streaks do not “owe” outcomes, read The Gambler’s Fallacy Explained (With Simple Examples).

Plan Bankroll and Session Size Using Variance

Odds tell you average cost. Variance tells you how rough the ride gets. High variance does not change house edge. It changes how quickly your bankroll can spike or crash.

• Set a session bankroll. Treat it as spent money. Do not reload to “get even.”
• Pick a base unit. Keep most bets at 1 unit. Large jumps increase swing speed.
• Set time and loss caps. Use a hard stop. Do not negotiate with yourself mid-session.
• Match game speed to your goal. Faster play reaches the long-run average faster. It also reaches the long-run losses faster.
• Respect bet volatility. Side bets, bonus buys, and longshot props raise variance fast.

If you play online, you face more outcomes per hour. That can make “short sessions” expensive. Game randomness still behaves the same. The machine just deals more hands. For the mechanics behind digital results, see Casino RNG Explained: How Random Number Generators Work.

Know When Strategy Changes the Edge

Some games let you reduce the edge with correct decisions. Others do not. Do not waste effort on systems in pure chance games.

• Strategy matters: Blackjack, video poker, some poker formats. Correct choices change your expected return.
• Strategy does not matter: Roulette, baccarat, slots, keno. Your decisions do not change the math unless you change the bet type.

Use this rule. If the game has decision points with different expected values, learn the correct chart or play guide. If the game only asks for a bet size and a bet type, focus on picking the lowest-edge option and controlling volume.

Treat Bonuses and Wagering Terms as Hidden Odds

A bonus can raise or crush your expected value. The real edge comes from the terms. Read them like a paytable.

• Wagering requirement. Higher playthrough increases your expected losses before you can withdraw.
• Game contribution. Slots may count 100%. Table games may count 10% or 0%. This changes the real cost of clearing.
• Max bet rules. A low cap can force slow clearing. A high cap can trigger forfeiture.
• Max cashout limits. A cap can cut off upside. It lowers your real EV even if you win big.
• Excluded games and providers. Your planned game may not qualify. Your effective choices shrink to higher-edge options.
• Time limits. Short windows push you into higher volume, which increases variance and likely losses.

Simple checkpoint. Estimate how much you must wager. Multiply required wagering by the house edge of the eligible game. That product approximates the expected cost to clear the offer.