What Is RTP?
Return to Player (RTP) is the percentage of all money wagered on a slot game that gets paid back to players over an infinite number of spins; it is not a promise of what you will win but the theoretical average calculated over billions of spins.
Example: A slot machine with a 96% RTP will pay back $96 for every $100 wagered over millions of spins; the casino will keep the remaining $4 as the house edge.
The critical word is theoretical. Over 200 spins of a slot, you might win your money back with a 150% return or lose all of it; there is no relationship between RTP and real world results of a session of a slot game.
How Is RTP Calculated?
The RTP of a slot game is calculated by mapping out every possible combination of slot reels and the probability of each combination occurring, multiplying each possible outcome by the probability of that outcome being hit, and dividing the total by the average bet size.
- Map every possible reel combination and its probability of occurring
- Assign a payout value to each combination
- Multiply each outcome's probability × its payout, and sum the results
- Divide by the average bet size to get the RTP percentage
Third-party testing laboratories calculate the RTP and publish certificates proving that the RTP is accurate; licensed casinos make these available upon request.
Why Jackpot Slots Are Different
Standard slot RTP rules break down for jackpot slots. Here's why:
The Jackpot Contribution Problem
All slots with progressive jackpots are funded by a portion of every bet placed on that slot; this amount is included in the RTP of that slot game. Hence, a slot with a 96% RTP might have an 88% base RTP but use the remaining 8% to contribute to a jackpot pool.
The portion of a jackpot slot game RTP that goes to the jackpot winner is paid out to only that player; all other players experience a base game RTP of 88%. Hence, unless you win the jackpot, which is extremely unlikely, the RTP you experience will be 88%.
What This Means Practically
- Never compare jackpot RTP to regular slot RTPJackpot slot games include the RTP contribution of the jackpot when calculating the percentage; hence, the RTP of a jackpot slot cannot be compared to that of a regular slot game.
- Ask for the base game RTP separatelySome developers publish the RTP of the base game of a jackpot slot game separately; hence, it is always a good idea to ask what the base game RTP is for a jackpot slot game before playing.
- Headline RTP can be misleadingA jackpot slot game with a 96% RTP may pay out less for you than another slot game with a 94% RTP.
- Higher jackpot contribution = worse base gameThe larger the jackpot contribution portion of a jackpot slot, the worse the base game experience for players who do not win the jackpot.
Variance vs RTP
RTP tells you the direction of money over an infinite number of spins. Variance (or volatility) tells you how rocky the journey will be.
- Low variance: Low variance means you will win frequently but small amounts; high variance means you will win less but larger payouts.
- High variance: Rare wins but bigger when they come. Long dry spells. Budget can disappear fast.
- Jackpot slots: Jackpot slots have a high variance as the jackpot you win is high but won very rarely.
For jackpot slots, variance should be considered in your session budget; you could lose your entire stake of money on a jackpot slot game before winning anything. Hence, only stake money that you are comfortable losing entirely.
Casino RTP Configurations
Most slot developers permit the casinos to configure the RTP within a specific range; hence, the same slot game may have a different RTP at two different Bitcoin casinos. We note the RTP configuration where we can verify it — see how individual games compare in our best Bitcoin jackpot slots rankings.