How Often Do Free Spins Trigger? Natural Bonus Frequency, Measured

Counting triggers instead of quoting odds

The frequency of a bonus is not on any help screen. It has to be counted, and the count has to exclude the buy button, because a purchased feature says nothing about the base game. Every test in the lab logs the round number of each natural trigger during its logged base run, with the buy button untouched and Ante off. Across 196 games with a self-triggering feature there are now 22,310 such triggers: one every 149 rounds on average, and one every 233 rounds for the median game. Tested games without a self-triggering feature, 2 at present, are left out of the counts.

The intervals, game by game

The chart takes the eight most frequent games and puts two marks on each row: the solid dot is the average spacing between triggers, the ring is the longest stretch that run went without one. On no row do the two sit close together. The longest wait reaches several times the average even for the games at the top of the ranking, because triggers arrive in bunches of two or three within a few dozen rounds and then leave blank stretches behind. That is the first thing to know about frequency: the average is a rate over a long run, not a rhythm.

The most frequent feature in the set belongs to Money Cart, which triggered 1,235 times in its run, one every 8 rounds. The least frequent is Hellcatraz, at one every 5,000 rounds. Between those two the interval differs by a factor of several hundred, across games declared between 95% and 99%: the return is similar, the route to it is not.

The longest waits

The number that decides a session is not the average interval but the longest gap. Across the lab, the longest wait between two natural triggers of the same game is 4,563 rounds, and the median game’s longest gap is 995 rounds. At a fixed stake, that gap multiplied by the stake is the turnover between two features in the worst stretch of the run, before any base-game wins are counted against it. A game that triggers once in 150 rounds on average can have a longest gap of 900, which is six average intervals of silence; each review lists its own longest gap under natural bonuses, so that the figure can be held against a session budget.

Frequency against payout

Frequent features tend to be cheaper features. In a scatter-pays or cluster game the bonus carries the multipliers, and a game that starts its feature often pays it modestly and keeps its base game thin; a game that makes the player wait tends to pay for the wait inside the feature. The average natural bonus in the lab returned 77 bets, but that average hides a range from a few bets to several hundred, and the games with the shortest intervals cluster at the low end of it. The free spins ranking sorts every test by interval and shows what each bonus paid alongside it, so that the two can be read as one trade-off rather than one number.

What Ante and the buy button change

Games with an Ante option claim a higher trigger chance for a higher stake, usually double for a quarter more per spin. Every count in this report was taken with that option off; whether the claim holds is a separate test the lab has not yet run, and it will be marked as such in the reviews when it exists. The buy button removes the wait entirely at a price of a hundred bets or more, and what that price returned is a different question with its own report: Is buying the bonus worth it? The two samples never mix. A purchased feature never counts as a trigger here, and a natural trigger never counts as a purchase there.

What this report will look like as tests are added

The chart, the tables and every figure above are recomputed from the current test set on each load. As the lab grows, the median interval and the spread of longest gaps are the values to watch: the median should move little, while the longest gap in the lab can only grow, because it is a maximum over an increasing number of runs. When a game is re-tested, its triggers and rounds are combined and its interval recalculated from the larger sample.