Progressive jackpot slots, with the maths
Progressive jackpots grow off every bet on the linked games, and the counter ticking up in the corner of the screen is that money. When someone wins, the pot resets to a seed, which is £1 million for the Mega pot in Mega Moolah. The base game pays less to fund all this, so Mega Moolah's listed RTP is 88.12%.
Where your bet goes
| Mega Moolah | A slot at 96.50%, no jackpot | |
|---|---|---|
| Paid back by the base game and free spins | $881.20 | $965.00 |
| Paid into the jackpot pots | $53.00 | $0.00 |
| Kept by the house | $65.80 | $35.00 |
| Your average loss if no jackpot lands for you | $118.80 | $35.00 |
Our calculation from the Mega Moolah split in the Casino.org review: 88.12% base return plus 5.3% to the four jackpots, 93.42% in total. SlotCatalog lists 88.12% as the RTP. Games Global does not publish the split on a product page we could find.
On Mega Moolah you lose about $119 per $1,000 of spins on average while you wait, more than three times the $35 a 96.5% slot takes. The other $53 isn't gone. It sits in the pots and goes back out to a handful of people in the millions, and to a lot more as Mini and Minor wins, which start at £10 and £100.
Tiers, seeds and the record
- Mega seed
- £1,000,000
- Major seed
- £10,000
- Minor seed
- £100
- Mini seed
- £10
- How a jackpot is won
- A wheel that starts at random in the base game, 20 segments, 1 of them Mega
- Biggest online slot jackpot on record
- €18,915,872.81 on 28 Sep 2018
- Earlier record, 2015
- £13,212,882, on a 25p spin
The 2015 win was £13.2 million, and the Mega pot starts at £1 million. Even if every penny of the 5.3% had gone to the Mega pot, that's roughly £230 million in bets across the linked casinos before it got that high. Some of it feeds the three small pots, so it was more.
Does a bigger bet win more often?
Per spin, yes. GLI-19, the online standard many regulators use, says the chance of a linked jackpot has to be proportional to the money you bet unless the game discloses otherwise. A $6.25 spin gets 25 times the chance of a $0.25 spin and costs 25 times as much.
| Bet | Jackpot chance per spin | Spins per $1,000 | Jackpot chance per $1,000 |
|---|---|---|---|
| $0.25 | 1x | 4000 | 1x |
| $1.00 | 4x | 1000 | 1x |
| $6.25 | 25x | 160 | 1x |
Our calculation under GLI-19 clause 4.13.4. Chance per spin relative to a $0.25 bet. The clause allows a variance of up to 5% on the probability. SlotCatalog notes that a bigger bet slightly raises the Mega Moolah jackpot chance.
If you're playing for the jackpot, a small stake over more spins gives you the same chance per dollar as a few big spins, and a lot more time. Read the jackpot section of the rules screen first. Where it names a minimum bet for the top pot, smaller spins can't win it.
Rules a jackpot has to follow
| Clause | Rule |
|---|---|
| 4.13.1 | A progressive pot rises with the credits wagered; an incrementing pot rises on set events in the game |
| 4.13.2 | The amount shown has to update at least every 30 seconds |
| 4.13.3 | A pot with a ceiling stays at the ceiling until won; extra money can go to an overflow pool |
| 4.13.4 | Linked jackpot chance proportional to the bet, unless disclosed |
| 4.13.5 | Part of each contribution may go to a diversion pool that funds the next seed |
| 4.7.1 c | The minimum RTP has to hold at the lowest jackpot settings |
The Stake Engine games in our data have no shared pot. Each mode has a fixed top prize in multiples of the bet, which you can compare on the max win page, and the chance of reaching it is part of the published maths rather than the size of a shared pot.
Not affiliated with Games Global, Casino.org, SlotCatalog or GLI. Game names belong to their owners. 18+, play responsibly.
Questions
How do progressive jackpots work?
A slice of every bet on the linked games goes into a shared pot. The pot grows until someone wins it, then resets to its seed. On Mega Moolah the seed of the top pot is £1 million.
Do progressive jackpot slots have a lower RTP?
The base game does. Mega Moolah pays back 88.12% outside the jackpots, with another 5.3% going into the pots, for 93.42% in total by review figures.
Does betting more increase the jackpot chance?
Per spin, yes, on linked jackpots that follow GLI-19: the chance is proportional to the bet. Per dollar wagered it stays the same.
What is the biggest progressive jackpot won online?
€18,915,872.81 on Mega Moolah on 28 September 2018, according to SlotCatalog, which cites the Guinness record.
Sources
- GLI-19 Standards for Interactive Gaming Systems v3.0 (PDF). section 4.13 progressive and incrementing jackpots, 4.7.1 c minimum RTP with jackpots Checked 12 November 2026
- Casino.org: Mega Moolah review. 93.42% overall = 88.12% base + 5.3% jackpots; wheel triggers at random Checked 12 November 2026
- SlotCatalog: Mega Moolah. RTP 88.12%, seeds £1m / £10k / £100 / £10, 20-segment wheel, release 28 Nov 2006, records £13,212,882 (2015) and €18,915,872.81 (28 Sep 2018) Checked 12 November 2026
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