Return to Player (RTP) and Variance in Casino Games
RTP and variance offer complementary ways to compare casino games. RTP describes the theoretical return; variance indicates how often a game may pay out and how large its payouts may be.
Understanding RTP
In casino terminology, RTP is comparable to the house edge, but it expresses the percentage returned to the player. RTP stands for “return to player.” Almost all slots have an RTP, while some table games list either RTP or house edge.
In theory, “house edge” can be expressed as “player edge,” with the latter representing a game's RTP. For instance, a blackjack table with a 0.5% house edge has a 99.5% player edge, or RTP. NetEnt Mega Joker, an online slot, has an RTP of 99%, which is equivalent to a 1% house edge.
As an online casino player, you will see that nearly all video slot games show an RTP. This figure helps slot players evaluate how often a slot may pay out on average.
How Is RTP Calculated?
RTP is based on the same mathematics as house edge, so the underlying equation is the same. As the blackjack example illustrates, a 0.5% house edge corresponds to a 99.5% RTP. Both figures come from probability.
The RTP of many table games was calculated when they were developed years ago. Blackjack, roulette, baccarat, and similar games fit this description. A casino may, however, add a side bet or introduce a rule change, either of which can affect RTP.
Online slots rarely share a single standard RTP. Their reels, pay lines, features, payouts, and symbol counts can vary considerably. Developers account for these factors and use a mathematical equation to determine the probability of each win when calculating RTP.
Understanding Variance
Variance, also called velocity here, describes how often a casino game may pay out and can give an indication of the size of a win. A high-variance slot typically pays less often than a low-variance one, but its winning payouts are generally larger.
Slots are often described as low, medium, or high variance, but all casino games have some degree of variance. Games such as craps and roulette offer several bets, each of which may have its own variance.
At roulette, an outside bet that pays even money or 2 to 1 is an example of a low-variance wager. Inside bets, in contrast, are medium- to high-variance wagers.
Here is a closer look at each category.
High Variance – Higher Risk, Higher Payout
These games do not typically deliver frequent small wins. A player may make several losing bets before a payout, but if play continues and a win arrives, it is generally much larger.
Roulette example: A straight-up roulette bet selects one number and has a 2.70% chance of winning, with a payout of 35 to 1. A win is unlikely on any single bet, but the potential reward is substantial.
Slots example: An online slot may go through a stretch with few winning symbol combinations, so players may need patience while waiting for its high-paying feature to trigger. That feature may take time to appear.
Medium Variance – Moderate Risk, Moderate Payout
These games combine smaller wins that can help sustain a bankroll and keep play interesting with a meaningful chance of a larger win at any time.
Roulette example: A roulette line bet covers six numbers, giving it a 16.2% chance of winning and a payout of 5 to 1.
Slots example: A medium-variance slot may award respectable base-game wins over time, with feature bonuses appearing with some regularity. Some such slots still pay infrequently in the base game, but their two bonus games place them in the medium-variance category.
Low Variance – Lower Risk, Lower Payout
These games are not usually known for large prizes. Wins may come frequently, sometimes in long streaks, though an individual win may not cover the stake. More commonly, the game regularly returns a percentage of the bet, with occasional wins multiplying the total wager value.
Low-variance games typically pay out often, but at low odds. This may describe a game with odds of 50/50 or near 50/50.
Roulette example: A bet on red or black has a 48.60% chance of winning and pays even money.
Slots example: Many 243-ways-to-win and Megaways online slots have low variance. Some regularly pay for symbol combinations, while their free spins features offer a small number of free spins that are easy to trigger. The result is frequent payouts, though the wins are usually modest.
Common Mistakes About RTP, Variance, and Variation
RTP is one of the casino world's most misunderstood concepts. The terms “variance” and “variation” are also often confused.
An RTP of 98%, for example, may seem to mean that every €100 wagered returns €98. That is not how RTP works; if it did, winning sessions or profits would be unusual. RTP is based on probability and is an estimate of how much a player is expected to win over an unspecified period of play.
Variation and Probability
Variation describes the ups and downs players may call “running hot” or “running cold.” RTP is the expected long-term return to the player. It does not mean that a €100 wager will reliably return €98, because variation affects both individual results and entire sessions.
These examples illustrate how variation affects probability:
Heads or Tails: In the familiar coin-toss game, the probability of winning is 50% because the mathematical odds do not change. Actual results vary: a player betting on tails might lose 40 of 50 flips, then win 85 tails bets in the next 100 flips. Results vary in every game of chance.
Dice: Dice show the same kind of variation. In theory, high/low or odd/even results should occur 50% of the time. A 6 should appear at least 16.67% of the time (1 in 6 rolls), yet 20 rolls might pass without a single 6.
Roulette: The same principles apply to French roulette. A player might keep betting on zero, which has a 37 to 1 chance (2.7% RTP) of appearing on the wheel, but 100 spins could pass without a zero before it lands on the next two coups.
Player Mistakes
Blackjack offers an example of how player decisions matter. Most blackjack tables have a 99.5% RTP, but that figure assumes basic strategy. Without it, a player can give back up to 5% to the house. Very poor decisions can forfeit 20% RTP or more—for example, splitting 10s despite holding a strong hand worth 20. Blackjack side bets further reduce RTP.
Variation in Online Slots
Slots differ from roulette in several ways. There is no baseline such as coin tosses, dice, or roulette probabilities, and slots do not have mathematical equations or charts like blackjack basic strategy. Slot outcomes are entirely random, so large wins depend wholly on luck.
Each slot uses an RNG (Random Number Generator) that processes several thousand reel combinations every millisecond. Pressing the button selects one of those combinations. The reels spin on screen for presentation and engagement; the result is determined when you press spin. The reels then stop at the randomly selected combination.
Online and land-based slots work in the same way. So the RTP displayed for slot games gives a rough estimate of your long-term return from playing that slot.
Summary
RTP indicates how much a casino game may pay back over time. “Variance” describes how often payouts may occur and may also indicate their size. RTP is a probability-based estimate of long-term winnings, while variation affects the amounts won and when wins occur.
