Online slot are great fun to play: they're easy to pick up, you can choose from a range of stakes, and the jackpots can be massive. For big players, progressive jackpot slots can pay out millions in winnings.

But all slots have one thing in common: they are governed by probability, the probability of winning symbols lining up on a payline. Of course, some slots have lower odds than others, with massive potential payouts to match. The job of the slots player is to work out which games offer the best chance of returns.

Getting Started: What Are Slots Odds?

Slot machines have been around for decades, and online and mobile gaming is close to outstripping real-money play in land-based casinos.

The sheer range of slots found online means players can log on and choose from 3-reel slots, 5-reel slots with bonuses, 7-reel slots for added thrills, and even dozens of progressive jackpots pooled across multiple casinos.

The aim in a basic slot is do one thing: line up matching symbols on a payline. Depending on the slot, there are several ways you can win:

  • Line up 2/3+ matching symbols on a valid payline
  • Land a 'Wild' symbol which substitutes for regular icons
  • Land a 'Scatter' symbol which pays regardless of where it hits

The payouts increase the more symbols you match. For instance, a slot might pay 2 coins for matching two identical symbols, 10 coins for hitting three identical symbols, and 50 coins for hitting four in a row. A jackpot of five matching symbols may pay 1000 coins.

But the actual odds of hitting winners will be far different to the payout, and will usually be much higher. 

How Slots Reels Are Set Up

Let's take a basic 5-reel online slot. The aim is to select paylines to bet on: these run horizontally left to right across the five reels. The more paylines you pick, the higher your stake. However, you will also be covering more options by betting more paylines on every spin.

You spin the reels, and a winner is paid if you match symbols on Reels 1, 2 and 3 (at least) on a set payline. Each reel is made up of fixed symbols, perhaps 20 in total but you might have six possible symbols in the game to aim for (the paytable will tell you what they are).

However, you won't know how many of each symbol is on each reel. This is set out in a slot 'PAR sheet' when the game is designed. You might find that low-paying symbols are stuck on the first reel, while the better payers are stuck out on Reels 4 and 5. If that's the case, the player will keep landing low-paying prizes over a long period. 

Example: Working Out A Slot Payout

So, can we work out the odds of hitting a winner? Let's take an example.

You are playing a 5-reel slot and checking the paytable you see that the lowest payer is the Bell symbol. It pays as follows:

Three Bells: 50 coins
Four Bells: 100 coins
Five Bells: 500 coins

Let's assume each reel has 20 symbols, and there are 3 Bell symbols on each reel. To hit three in a row, the odds are 3/20 x 3/20 x 3/20, or 27/8000 - just under a 1 in 300 chance. But the payout is only 50 coins, or 50/1. The discrepancy is where the slot has its edge over players.

Some 5-reel slots have Wilds, which substitute for regular symbols to help 'fill the gaps' on a payline. If there are lots of Wilds on the reels, the odds of hitting your winning payline will reduce.

Of course, you won't know the exact arrangement of each reel unless you've played a game a lot. However, you can get an overall idea of how good a game is by checking the RTP.

Understanding RTPs (Return to Player Percentages)

The RTP, or Return to Player percentage, is the expected long-term payout share made to players. The higher the RTP, the better it is for players.

For example, a typical online slot has an RTP between 92 and 98 percent. In a 98% slot, then, $0.98 is returned to players for every $1 wagered. Of course, players may be betting with $1 of money they actually won on the previous spin, so in effect they are simply ploughing winnings back into the game.

You can check the RTP in the slot paytable; most games will display it. If not, you can sometimes find it in the casino lobby instructions or listed on an external audit report. Again, most good casinos will let you read the independent audits. These are tests made by external labs who put the slots through their paces.

The RTP is just a guide. If you play enough slots for long enough, you will end up a loser. The house edge ensures that players are on the losing end over a long period. But some slots are more volatile than others.

Volatility is a tricky concept, but simply it's the frequency with which slots pay out. High-volatility slots may pay nothing for 50 spins before hitting a massive jackpot. Low-volatility slots, meanwhile, will pay little and often without any major jackpots landing.

Volatility is down to the arrangement and frequency of symbols on the reels.  Again, playing enough of one slot will help you decided if a game is volatile or not.

Tips On Winning More From Slots

Try Games Out First: It's important to work out before you play what you want out of your games. Do you have enough bankroll to handle long periods of no wins? If so, a high-volatility slot might be for you. If you want excitement and action, a bonus slot with lush graphics and animated reels is for you.

Work Off A Bonus: Casino bonuses will usually always allow slots play to contribute. The more you play, the faster you can "play through" a welcome or reload bonus. By picking the right slots with bigger jackpots, you can work off a free-cash bonus more quickly.

Quit When You're Ahead: Winning spins are actually less frequent than you might think. Naturally, players tend to remember their big jackpots rather than the money they've lost.

It's important to take the money when you can. While it's tempting to gamble the $100 win back on the slot, the odds will ensure it disappears eventually. So always try to cash out big wins and 'reset' your original bankroll. That way you won't be tempted to lose any significant wins. 

Online Slots Odds FAQs 

What Are Slots Odds?

Odds are the probability of hitting a winning combination in an online slot.

Are All Online Slots The Same?

No, the odds and payouts vary massively from slot to slot. It's important to check a Paytable first to see how generous the jackpots are. Then, play plenty of free-money spins to get a feel for the slot's win frequency.   

How Can I Find Out A Slot's RTP?

Most Paytables will display the RTP (Return to Player percentage). This gives an indication of the long-term payouts made to players. An RTP can also give you a rough gauge of how often winning symbols line up across the reels.  

What's The Best Way To Win At Slots?

Quitting while you're ahead is vital to maintaining a bankroll. Choose slots with high RTPs, and never exceed your bankroll. You should have enough cash to last 100 losing spins if needed.

Are Progressive Jackpots Good To Play?

Yes. Progressive jackpot slots can pay out jackpots worth hundreds of thousands, or millions, of dollars. Usually, players will have to be betting the maximum stake in order to qualify. However, they can be very volatile and should be reserved for big bankrolls only.

What Are Volatile Slots?

Volatile online slots tend to pay out big wins infrequently. Players may find themselves on a long losing run before hitting a jackpot.