Slot guide
Big Thunder slot review: Ainsworth's 30-line game with a sixth bonus reel
Ainsworth's 2017 slot with adjustable lines, stacked wilds, scatter free spins and an extra bonus reel worth up to 10,000x the line bet.
Big Thunder is Ainsworth's 2017 video slot: five reels, three rows and up to 30 lines, with a published RTP of 94.38%. Its signature is a special sixth reel carrying bonus prizes worth up to 10,000x the line bet, alongside stacked wilds and scatter-triggered free spins. Volatility and maximum win are reported differently across game databases, so neither is quoted on this Big Thunder slot page.
Big Thunder: spec sheet
From the provider's published game sheet.
- Provider
- Ainsworth
- RTP
- 94.38%
- Reels
- 5
- Rows
- 3
- Lines
- 30
- Min bet
- 0.30 credits (all lines)
- Max bet
- 3,000 credits (100 per line)
- Released
- 2017
Features
- Adjustable lines: 1, 2, 3, 5, 10, 15, 20, 25 or 30
- Stacked Wilds
- Free spins with scatter symbols
- Special 6th bonus reel with prizes up to 10,000x line bet
RTP can be set lower by some casinos; the game's own help screen shows the figure that applies. 18+ only.
Choosing how many lines to play
Unlike most modern games, Big Thunder lets you pick 1, 2, 3, 5, 10, 15, 20, 25 or 30 lines. Bets are shown in credits: from 0.30 credits across all lines up to 3,000 credits at 100 per line. Fewer lines mean a lower total stake but fewer ways to connect symbols, and because the bonus reel pays in multiples of the line bet, the line setting also changes what those prizes are worth in pounds.
Stacked wilds, scatters and the sixth reel
Stacked Wilds can cover a whole reel and help complete several lines at once. Scatter symbols trigger the free spins round, and the extra bonus reel beside the main grid adds prizes of up to 10,000x the line bet. The in-game paytable explains how many scatters are needed and how the bonus reel comes into play in the build your casino carries.
Big Thunder RTP and the versions to tell apart
The 94.38% figure applies to the original 5x3, 30-line game. Some listings also print 96.27%, which is a reminder to read the RTP inside the game itself; the RTP guide explains why builds differ. Big Thunder MegaLoot, with 50 lines, and Big Thunder Quad Shot are different games, not settings of this one. There is no bonus buy among the original's listed features, so a search for a Big Thunder bonus buy usually concerns a spin-off.
Playing Big Thunder in the UK
At GB-licensed casinos the most you can stake on an online slot is £5 per game cycle, or £2 if you are 18 to 24, whatever the credit range in the paytable; the stake limits guide has the detail. The licensed casinos reviewed here do not name Ainsworth among their suppliers, so no casino is shown beside this review; search a licensed casino's lobby for the title or the studio instead. This site hosts no Big Thunder demo. Free play, where offered, comes from a licensed casino's demo mode after age and identity verification, which GB rules require before any game is opened.
Bonus spins offers list the games they can be used on, and an older title may not be one of them; the free spins bonuses guide shows what to check in the significant terms. 18+ only; read the responsible gambling page for limits, time-outs and help.
Questions readers ask
Which studio is behind the Big Thunder slot?
Ainsworth, which released it in 2017.
How many lines does Big Thunder have?
Up to 30. You can play 1, 2, 3, 5, 10, 15, 20, 25 or 30 lines.
What does the sixth reel do?
It is a special bonus reel with prizes of up to 10,000x the line bet.
Why do some sites show a different Big Thunder RTP?
The original 30-line game is listed at 94.38%. One site also prints 96.27%, but its own data box says 94.38%, so the help screen at your casino has the final word.
Is Big Thunder the same as Big Thunder MegaLoot?
No. MegaLoot has 50 lines, and Big Thunder Quad Shot is another separate game.