How cascading reels work

How cascading reels work, in one paragraph

On a standard slot, the reels stop, any wins are paid and the round is over. A cascading slot adds a loop. After the wins are paid, every symbol that formed part of a win disappears. Gravity takes over: the remaining symbols slide down, and fresh symbols drop in to fill the empty spaces. The game evaluates the new screen exactly as it did the first one. If there's another win, the loop repeats. If there isn't, the spin ends and you can press the button again.

Different studios brand the same idea differently. NetEnt called it Avalanche on Gonzo's Quest, Pragmatic Play calls it Tumble on Sweet Bonanza and Gates of Olympus, and Big Time Gaming uses Reactions on Bonanza Megaways. Underneath the names, the logic is the same: wins remove symbols, the grid refills, the game checks again. The cascading reels glossary entry gives the short definition; this guide shows what happens inside a chain and what it means for your balance.

A cascade chain, frame by frame

Picture a 5 × 3 game with 20 paylines, played at 50p a spin. The numbers below are made up to show the mechanics, not taken from any real paytable.

1. You press spin and pay 50p. The reels land with three crowns on line 4, worth 0.5x stake. The game credits 25p.
2. The three crowns explode. The symbols sitting above them slide down into their positions, and three new symbols drop into the top row.
3. The new layout happens to line up four rubies on line 11, worth 1x stake. Another 50p is credited, so the chain has now paid 75p.
4. The four rubies vanish and the grid refills again. This time nothing connects on any of the 20 lines.
5. The chain stops. The win panel shows 75p for the whole spin, and your net position for the round is +25p.

Two things are worth noticing. First, you were charged once. Every refill after the first drop is part of the same bet. Second, the game shows a single total at the end. That total is what the game history records and what UK rules care about when deciding whether a result can be celebrated, which we come back to below.

The maths behind long cascade chains

Each refill is a new draw of random symbols, so the chance of the chain continuing is roughly the chance of a win on a partially fresh screen. If a refill produces a fresh win 30% of the time, the odds of the chain running a given number of extra steps fall away fast, because each step needs another 30% event.

Real games don't have one fixed continuation rate. Symbols that fall in are partly the leftovers from the previous screen, which can make a second win slightly more or less likely depending on what stayed behind. But the shape holds: short chains are common, long chains are rare, and a run of eight or nine cascades is an unusual event rather than something to expect. With a 30% continuation rate, the average number of extra cascades after a winning spin is 0.3 ÷ 0.7, or about 0.43.

A long chain doesn't change the odds of the next spin. The RNG has no memory, so the following spin starts from scratch.

Cascade multipliers: where the chain earns its keep

On its own, a cascade only adds the occasional extra small win. Most cascading slots pair it with a multiplier that climbs as the chain grows, and that pairing is what creates the big outcomes. Gonzo's Quest is the classic example: in the base game the first win pays 1x, the second 2x, the third 3x and the fourth and later 5x. During the Free Falls feature the ladder runs 3x, 6x, 9x and 15x.

Here is what that ladder does to a run of identical 20p line wins at a 50p stake:

Bonanza Megaways takes a different route in its free spins: the win multiplier rises by one with every cascade and doesn't reset between spins of the feature, so a long feature can build a large multiplier. Sweet Bonanza and Gates of Olympus use separate multiplier symbols that land during the tumble sequence and are added up and applied once the chain ends. Our guide to how multipliers work in slots breaks down each style with numbers.

How cascades fit different pay systems

Cascades sit on top of whatever system the slot uses to decide what counts as a win.

• Paylines. Only symbols on a winning line disappear. Gonzo's Quest works this way on 20 lines.
• Ways and Megaways. Every matching symbol in the winning ways is removed, which can clear a big chunk of a 117,649-way screen at once. How Megaways works covers the changing reel heights.
• Cluster pays. Groups of touching symbols vanish, as on Reactoonz and Jammin' Jars. Chains on cluster pays grids are often longer because refills create new contacts in two directions.
• Pay anywhere. Any eight or more matching symbols anywhere on the screen pay, then vanish, as on Sweet Bonanza. The pay anywhere model makes refills feel especially swingy because a whole symbol type can clear at once.

Well-known cascading slots compared

The figures below are each game's published default or top RTP. Your casino may run a lower version, so always check the game's help screen before you play.

Notice how few of these are low volatility. Cascading games tend to hold back a lot of their return for long chains with rising multipliers, which makes them swingier than a plain line slot like Starburst. Browse more in our cascading reels slots collection.

Do cascading reels pay more? RTP and volatility

No. The studio builds the whole chain into the game's maths model before release. Every possible cascade, multiplier step and refill is part of the calculation that produces the published RTP. A 96.5% game returns, over a very large number of spins, about £96.50 for every £100 staked, whether that return arrives as single wins or as chains. Cascades change how the return is distributed, not how big it is.

What cascades usually do is push volatility upwards. Because some of the return is reserved for rare long chains, the remaining spins pay a bit less often or a bit less on average. In practice, 200 spins at 20p (£40 staked) on a high-volatility cascading game can easily end well below £40 with no chain longer than two steps, while another 200-spin session could produce one chain that pays more than the whole £40. Neither outcome tells you anything about the next session.

UK rules that shape cascading games

Cascading slots sold to British players follow the same game design rules as every other slot, and a few of them matter more here than usual:

• 2.5 seconds minimum per spin. The rule applies to the time between one spin starting and the next being possible. Long cascade animations simply make some spins last longer; there's no turbo or quick-spin option to cut them short.
• No celebrating losses. If a chain pays less than you staked, for example 30p back from a 50p bet, the game can't play win music or animations that suggest you've won.
• Net position on screen. Your session's running gain or loss stays visible, which helps when a lively chain makes a losing session feel better than it is.
• Stake limits. The £5 per spin limit for players aged 25 and over, and £2 for those aged 18 to 24, cover the spin, and the cascades cost nothing extra.
• No bonus buys. In Great Britain you reach the free spins with rising multipliers only by landing the trigger symbols naturally. See how bonus buys work for what the option is elsewhere.

The full picture is in our guide to UK slot game design rules.

Cascade myths, checked

For more beliefs tested against the maths, see slot myths.

What to check on a cascading slot before playing

1. Open the info screen and find the RTP figure for the version your casino runs. Our guide to reading a slot's game info screen shows where it sits.
2. Read how the multiplier behaves: does it reset after every spin, or carry over during free spins? This is the single biggest difference between cascading games.
3. Look for a cap on the multiplier and the game's max win, both stated in the rules.
4. Note the volatility rating if the studio publishes one, and set your session budget with it in mind.
5. Try the demo after age verification to see how often chains actually run past two steps.

18+. Gambling should be entertainment that costs money, not a way to make it. Set a deposit limit before you play: how to set limits. Free, confidential help: National Gambling Helpline 0808 8020 133.