Return-to-Player (RTP) & Variance in Casino Games
RTP and variance work together when comparing casino games. RTP describes the theoretical return, while variance indicates how frequently a game may pay and how large those payouts may be.
What is RTP?
In casino terms, RTP is comparable to the house edge, but it expresses the percentage advantage assigned to the player. The initials mean ‘return to player’. Nearly all slots carry an RTP, whereas some table games display either RTP or house edge.
In principle, ‘house edge’ could be reframed as ‘player edge’, with that player edge representing a game’s RTP. For example, a blackjack table with a ‘house edge’ of 0.5% would have a ‘player edge’ or ‘RTP’ of 99.5%. Likewise, NetEnt Mega Joker online slot game has an ‘RTP’ of 99%, which can also be described as having a ‘house edge’ of 1%.
As an online casino player, you will find that nearly all video slot games display an RTP. This figure gives slot players a way to assess how frequently an online slot may pay out on average.
How Is RTP Calculated?
RTP uses the same mathematical basis as house edge, so there is no difference in the underlying equation. As the blackjack example shows, a 0.5% house edge converts readily into a 99.5% RTP. Both figures are derived from probability.
Many casino table games had their RTP calculated when the games were created years ago. Blackjack, roulette, baccarat, and similar games fall into this group. However, a casino may sometimes introduce an additional side bet or rule, and either change can alter the RTP.
Online slots, by contrast, seldom share one standard RTP. Their reels, pay lines, features, payouts, and symbol counts can vary frequently. To calculate RTP, the developer must account for all those variables before using a mathematical equation to establish the probability of each win.
What is Variance?
Variance, also referred to as velocity here, describes how frequently a casino game pays out and can suggest the size of a win when one occurs. A high-variance slot generally pays less often than a low-variance slot, while its successful payouts are usually larger.
Casino discussions often classify slots as low, medium, or high variance, but every casino game has some level of variance. Games such as craps and roulette offer multiple bets, and each bet may carry its own variance.
On a roulette table, an outside bet paying even money or 2 to 1 is an example of a low-variance bet. Inside bets, by comparison, represent medium- to high-variance wagers.
Each category is explained in more detail below.
High Variance – High-Risk High Payout
These games do not usually produce frequent small wins. Several bets may pass without a win, but when a payout eventually arrives, it is generally much larger, assuming play continues.
Roulette Example: A straight bet in roulette selects a single number, carrying a 2.70% chance of winning for a 35 to 1 payout. The win is unlikely on any individual bet, but its potential reward is substantial.
Slots Example: An online slot may produce few symbol combinations for a while, requiring patience until its high-paying feature triggers. Reaching that feature could take some time.
Medium Variance – Medium Risk Medium Payout
These games combine smaller wins, which can help maintain a bankroll and keep play engaging, with a meaningful possibility that a larger win will appear at any point.
Roulette Example: In roulette, a line bet covers six numbers, providing a 16.2% chance of winnings and a 5-to-1 payout.
Slots Example: A medium-variance slot may deliver respectable base-game wins over time, while its feature bonuses can arrive with some regularity. Some such slots still pay infrequently in the base game, yet their two bonus games place them in the medium-variance category.
Low Variance – Low-Risk Low Payout
These games are not generally associated with large prizes. Wins may arrive frequently, sometimes in extended streaks, although an individual win may not cover the stake. More often, the game returns a percentage of the bet regularly, with occasional wins multiplying the bet’s total value.
A low-variance game tends to pay frequently at low odds. This description can apply to a game where the odds are 50/50 or close to 50/50.
Roulette Example: Betting on red or black gives you a 48.60% chance of winning, and the bet pays at even odds.
Slots Example: Many 243 ways to win and Megaway online slots are low variance. Some regularly award symbol-combination wins, while their free spins games offer a low number of free spins that are easy to trigger. This produces frequent payouts, although the wins are usually modest.
The Biggest Mistakes Players Make with RTP, Variance, and Variation
RTP is among the most misunderstood casino concepts. The terms ‘variance’ and ‘variation’ are also regularly mixed up.
An RTP of 98%, for example, might appear to mean that every €100 wagered will return €98. That interpretation is incorrect, and such a fixed result would make winning sessions or profit unusual. Because RTP is probability-based, it is an estimate of the amount a player is predicted to win over an undefined period while playing a game.
Variation/Probability
Variation describes the upswings and downswings that players may call 'running hot' or 'running cold'. RTP is the expected long-run return to the player. It does not mean that betting €100 will consistently return €98, because variation changes both individual results and sessions.
These examples show how variation can affect probability:
Heads or Tails: In the familiar game of heads or tails, the RTP for winning is 50%, because mathematical probability does not change. Results, however, are not constant: a player could bet on 'tails' and lose 40 times out of 50 flips, then win 85 'tails' bets over the next 100 flips. Every game of chance has variations in its results.
Dice: Dice produce the same kind of variation. In theory, probability indicates that high/low or odd/even should occur 50% of the time. A 6 should appear at least 16.67% (1 in 6 rolls), yet 20 rolls could pass without producing a 6.
Roulette: The same ideas apply to French roulette. A player might repeatedly bet on zero, which has a 37 to 1 (2.7% RTP) chance of appearing on the wheel, yet 100 spins could pass without zero before the next two coups suddenly produce it.
Player Flaws
Blackjack illustrates a player flaw. Most Blackjack tables have an RTP of 99.5%, but that calculation assumes basic strategy. Without it, the player can give the house back up to 5%, while very poor decisions can surrender 20% RTP or more, such as splitting 10s despite holding a strong hand worth 20. Playing Blackjack side bets reduces RTP further.
Online Slots Variation
Slots differ somewhat from roulette. There is no heads/tails, dice, or roulette probability baseline to use, nor are there the mathematical equations or charts associated with blackjack's basic strategy. Slots are entirely random, so large wins depend wholly on luck.
Each slot uses an RNG (Random Generator) that runs several thousand-reel combinations through the system every millisecond. Pressing the button selects one of those combinations. The visible reels spin only as part of the presentation, making the game more engaging; the result was already determined when spin was pressed. The reels then stop on the randomly selected combination.
Online and land-based slots operate in the same way. Therefore, the RTP shown for slot games offers a rough estimate of your long-term return by playing that slot.
Summary
RTP indicates how much a casino game may pay over time. ‘Variance’ describes how often payouts may occur and can also suggest their size. RTP remains an indication of predicted long-run winnings based on probability, while variation affects the amounts won and when those wins occur.
