Slot RTP Explained

OK, slot RTP explained is quite simple, yet complex as I will explain. Let’s say we design a slot game with 5 reels and 3 rows which is pretty normal. Each reel has 100 symbols on and randomly stops. You have 10,000,000,000 (10bn or 100*5) possible outcomes! The game has 20 paylines though, so there are now 500 million permutations (10bn/20).

Let’s say that if you spent 1 Euro on a spin and got all possible outcomes ONCE, you would get 480,000,000 back. That is 96% of your 500m so the THEORETICAL RETURN TO PLAYER (TRTP) is 96%. Pretty average for most games. This includes any 2,3,4 or 5 reel wins on any of the 20 paylines. This is the simple bit about slot RTP!

Slot RTP and Variance Taken Into Account

Now variance is added. Let’s say ALL spins won and ALL winning combinations paid 96c. So you’d have the most boring game ever as you’d win 96c on every spin for your 1 Euro. Your RTP line would come out from the the vertical axis on the left of your graph at 96 horizontally. It would never move therefore you have zero-variance because your slot RTP equals the TRTP forever! (You’ve all played St*rb*rst?)

Now we do the opposite – ALL permutations pay zero except one which pays 480m x stake! If you hit this on the first of your 500m spins your RTP (remember RTP is a temporary figure!) would be after that spin 48 billion percent! Your RTP line would go off the graph vertically past the 96 marker and stop somewhere near the moon. Should you hit this on the last of the 500m spins then your graph would be flat along the horizontal axis for miles until you hit that win and it spiked up vertically to 96%.

Theoretical RTP and Stated RTP

It does confuse things when some slot developers have their TRTP in the information section and call it RTP. Whether the slot states RTP or TRTP is always the THEORETICAL return to player they are referring to. (see Ruby Slippers photo below, the TRTP is 95.96%)

Slot RTP and Volatility

A low-variance or volatility game would have say 30-40% of all possible outcomes awarding a win, but a very low one say 0.1-2x stake with rarer ones paying higher. A higher-variance or volatility game will have infrequent wins (say 1/12 spins and most will be low too) but pay tens or hundreds x stake for some combinations. Think Microgaming’s Break Da Bank Again. It all depends on what value the programmers or software developers attribute to the symbols on the reel maps and their frequency on the reels.

Bonus Rounds and RTP Allocation

So, you’ve been waiting to ask, what about bonus rounds? Quite simple. In my example all permutations ONCE award 96% of the total 500m stake. Let’s say we got all winning permutations once and our RTP after doing so was only 70% – why? Simply because some of those outcomes would be 3 or more scatters which award bonus rounds, and these bonus rounds are set to award 26% of the TRTP. So about a quarter of any returns you get over time would be down to triggering bonus rounds. On games like Netent’s Dead Or Alive the bonus round itself is very high variance too which is why you get quite low variance in the base-game and yet can hit massive 1000’s x stake in the bonus spins. Despite the big reward potential, the DoA free games round forms slightly less of the overall TRTP than it does on say Thunderstruck2.

On some games you will see the TRTP as a variable figure, say 96.15-97.0%. This is because it may have side-bets which increase RTP slightly or has random bonus rounds which can’t be calculated accurately as the combinations are so vast it’s impossible to state exactly the long-term TRTP other than a small range within say 1%.

SO what is my RTP?

If you deposit 100, play 100 x 1-Euro spins and get back 80 Euros, it’s 80%. RTP unlike TRTP is transient, dynamic. Now play that 80 Euros back at 1 Euro a spin and win back 90 euros. You have now had 180 spins and won back 170 Euros. Therefore your session RTP is now 17/18 = 94.44%. Many players make the mistake of playing until bust over hundreds of spins and then complain that their ‘RTP Is bad’ etc… Simply not true.


So imagine the graph again with the TRTP 96% line coming out horizontally from the vertical axis. On a low-variance game your outcomes will appear slightly above and below that line in undulating cycles of winning and losing spins. On a high-volatility game these peaks and troughs will be far more pronounced – long stretches of the wavy line being positioned well below the 96% TRTP one and then spiking up well above that line when the large wins appear (if ever!)

RTP Over Time

Many players complain their slot RTP is low, and tend to exaggerate the number of games they play. Remember my example – to see the TRTP you’d need 500m spins! I doubt if many players have even played 500 thousand games on any one slot at any one site – that’s one-thousandth of the amount of spins the TRTP is calculated over in my scenario! This is why the slot RTP you have as an individual deviates so much from the TRTP in many cases. The higher the variance the more spins it will take to closely match the TRTP with your personal RTP on the slot. On low-variance slots you’ll be pretty much near the 96% from very early on.

In the end, it’s all down to luck – it’s gambling after all!