Casino bankroll calculator & risk simulator
The house edge sets the average. Volatility decides how wild the ride is. This shows both.
The model and its assumptions
- Two-outcome bets. Each bet either wins
RTP / ptimes the stake with probabilityp, or loses the stake. That makes the long-run return exactly the RTP you enter. - Volatility = how rare the wins are. Low: p = 49% (≈2x wins, like even-money dice). Medium: p = 20%. High: p = 2%. Extreme: p = 0.2% (≈480x wins at 96% RTP). Real slots mix many small and a few huge payouts, so use the presets as a rough range, not a model of a specific game.
- Flat betting. Same bet every time; no martingale or bet changes. A session stops if the bankroll can no longer cover a bet.
- Independent rounds. Each bet is independent, which is how RNG and provably fair games are designed.
- Seeded and reproducible. The simulation uses a seeded pseudo-random generator (mulberry32) and runs in small chunks in your browser, so the page stays responsive. Nothing is sent anywhere.
expected loss = N x bet x (1 - RTP) stdev per bet = bet x sqrt(p x payout^2 - RTP^2) stdev over N bets = stdev per bet x sqrt(N)
The expected loss grows with N; the typical swing grows only with √N. That is why short sessions feel random and long ones converge on the house edge. More in house edge vs RTP vs volatility. If the numbers here worry you, see responsible gambling.