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Estimate how much a bonus feature adds to a game's RTP from how often it triggers and what it pays on average — then see whether the whole game clears break-even at your bet.
Trigger Frequency
How rare the feature is, as 1 in N spins
Average Feature Win
Average TOTAL payout per trigger — duds included
Bet Size
What you wager per spin
Base RTP (excl. feature)
Base-game return with this feature excluded
Get the Average Feature Win Right
The average feature win must be the TOTAL payout averaged over ALL triggers — including the small, zero-ish dud features — not a typical big hit. Over-estimating it is the #1 way people fool themselves into a -EV game. The base RTP must also EXCLUDE this feature, or the return is double-counted. Borderline (98–100% total RTP) is still negative EV — just close to even.
-$0.06
Return: 94.50%
Total RTP
94.50%
Below 100% — on average the game keeps a slice of every dollar wagered.
Total RTP is well under 100% — the feature doesn't pay enough, often enough, to clear break-even.
Feature RTP Contribution
12.50%
How many RTP points the bonus feature adds: trigger chance × average payout ÷ bet.
EV / Spin
-$0.06
Average loss of $0.06 on each spin.
EV / 100 Spins
-$5.50
Expected result over a typical 100-spin session at this bet.
Inputs
How rare the feature is — 1 in 120 spins means p = 1/120 per spin.
Average TOTAL win per trigger at your bet — averaged over ALL triggers, duds included.
What you wager per spin.
Base-game RTP EXCLUDING this feature. Must exclude it, or RTP is double-counted.
The feature's contribution to return is just trigger chance × average payout ÷ bet. Add that to the base-game RTP (with the feature excluded) to get total RTP. If total RTP clears 100%, the game is +EV at your bet; below that, every spin loses a little on average.
Use the AVERAGE feature win including the small, disappointing triggers — not a typical big hit. Over-estimating it is the #1 way people fool themselves into a -EV game.