Enter your bankroll, your average bet, the RTP of the game and its volatility. The calculator estimates how long that bankroll lasts — in spins and in sessions — and how deep a losing run it survives before the balance is gone.
Bankroll arithmetic, in plain English
The house edge of a game is the slice of every bet the casino keeps on average — the inverse of the published RTP. At 96% RTP the edge is 4%, meaning every euro you put in returns ninety-six cents on average and the casino keeps four. Multiply that edge by your average bet and you have your expected loss per spin. Divide your starting bankroll by that number and you have the spins you can expect before the edge eats it.
Expected is not guaranteed. Volatility is the size of the swings around that average. A high-volatility slot might leave you with the full bankroll after fifty spins, then drain it in twenty — or never pay a meaningful hit at all in your session. We use volatility to scale a survival probability: the chance your bankroll outlasts the session you planned. For a recommended max bet we cap single-spin exposure at a small fraction of your starting roll so a deep losing streak does not end the night on spin three.
None of this predicts the next spin. It tells you what is reasonable to expect across a large number of them — useful for sizing bets to a bankroll, not for chasing losses.
How survival time is estimated
The expected loss per spin is your bet multiplied by (1 − RTP): 2 at 96% costs 0.08 a spin on average, so 500 covers roughly 6,250 spins if nothing unusual happens. Nothing unusual is the catch, and that is what volatility adds. A high-variance game delivers the same average through rare large wins, so the swing around that line is wide and the bankroll can be gone long before the arithmetic says so.
The model is deterministic and published here: expected loss sets the slope, the volatility band sets how far a realistic run can fall below it. Inputs are validated in application code; editors cannot change the formula.
FAQ
What bet size fits my bankroll?
A common working rule is a bet no larger than 0.5% of the bankroll on a high-volatility slot and 1% on a low-volatility one. Enter both and compare the spin counts rather than taking a rule on faith.
Why do two games with the same RTP give different answers?
Because volatility changes the spread, not the average. The low-variance game spends the bankroll slowly and steadily; the high-variance one can end it in a short run of dead spins.
Does a bonus extend the bankroll?
Only if you can clear it. Use the wagering calculator first: a bonus with a high requirement can cost more to unlock than it adds.
Is this a strategy?
No. It sizes a bet against a budget. No bet size changes the house edge, and raising stakes to recover a loss only raises the expected loss.