Bankroll maths, 2026
How long will your money actually last?
Set your budget, your stake and how long you want to play. The calculator runs thousands of simulated sessions for your chosen game and shows your likely result, the realistic range, and how often the money runs out first.
Slot results use the same three model games as our simulation research. Real slots vary, so check each game's RTP and volatility.
What is risk of ruin?
Let's start with a clear definition. Risk of ruin is the chance that your budget hits zero, or drops below the size of your next bet, before you've played as long as you meant to. It's the number most players never think about, and it explains a lot of sessions that feel unlucky but are actually just maths.
It's different from the house edge. The edge tells you what a game costs on average over a very long time. Risk of ruin tells you how likely you are to get knocked out along the way, and that depends on how much your results swing from bet to bet. Two games with the same edge can have wildly different risks of ruin.
How does this bankroll calculator work?
Rather than rely on a formula that only works for evenly spread results, the calculator plays out thousands of sessions in your browser. Each spin or hand is drawn from the real outcome table for that game: 18 winning pockets out of 37 for red, the published hand frequencies for 9/6 Jacks or Better, and so on. A session stops early if the budget can't cover the next stake.
The slot options use three model games, each paying back exactly 96%, with low, medium and high volatility. They're the same models used in our simulation research, where you can see their full pay tables. Blackjack uses a simplified outcome table matching basic strategy's roughly 0.5% edge, including blackjacks, doubles and pushes. Because the sessions are random, the figures move slightly each time you press run again. That wobble is normal.
Why does your stake matter more than the game?
This is the part that surprises people. Take a £100 budget on European roulette, betting red for 200 spins. At £1 a spin, the typical session finishes around £6 down and the money essentially never runs out. At £5 a spin, the same 200 spins cost around £25 on average, and about one session in four runs out of money first.
The game didn't change, and neither did the edge. What changed is the size of each swing compared with the budget. The thing is, most players pick their stake based on what feels exciting rather than what the budget can absorb. A simple rule that holds up well: if you want a session of a few hundred bets to survive most of the time, keep each stake to around 1% or 2% of the budget on low-swing games like red or black, and lower still on slots.
How much budget do slots really need?
Much more than table games, because of volatility. Using the model slots, a £100 budget at £1 a spin for 500 spins runs out about 14% of the time on the low-volatility game, about 45% on the medium one, and about 80% on the high one. All three have exactly the same 96% RTP.
Drop the stake and the numbers change quickly. The medium-volatility slot at 50p a spin runs out only around 7% of the time over the same 500 spins, and the high-volatility slot at 20p a spin rarely does. If you're playing a high-volatility game for its big features, a smaller stake is what gives you enough spins to have a realistic chance of seeing one. The slot volatility page covers how to spot a game's volatility before you play.
Do betting systems lower your risk?
No, they move it around. Martingale, doubling your bet after every loss, makes small wins very likely and big losses rarer but much bigger. In our simulation of 10,000 Martingale sessions on roulette with a £200 budget, about 76% reached a £50 profit, and about 24% lost the full £200. The average session still lost around £10, which is exactly the kind of result the house edge predicts. The full numbers are on the casino simulations page.
The same applies to every progression, from Fibonacci to D'Alembert. They change the shape of your results, never the average. If a system claims to reduce your risk of ruin while keeping your expected win the same, it's claiming something the maths doesn't allow.
Where does AI come into bankroll decisions?
Mostly on the casino's side. Operators' safer gambling models watch for the signs that a budget isn't being respected: repeated top-up deposits, cancelled withdrawals and chasing losses. In the UK, the Gambling Commission is also bringing in financial risk assessments for very high spending, covered on the responsible gambling AI page. None of that replaces setting your own limit before you start, which is what this calculator is for.
What should you do next?
Decide the budget first, then pick a stake the budget can carry.
FAQ
What else do people ask about bankroll and risk of ruin?
What is risk of ruin in gambling?+
It's the chance that your budget runs out, or drops below your next stake, before you finish the session you planned. It depends on the house edge, the game's volatility and the size of your stake compared with your budget.
How much bankroll do I need for roulette?+
It depends on your stake and session length. Betting red at £1 a spin for 200 spins, a £100 budget almost never runs out. At £5 a spin, the same budget runs out about a quarter of the time.
Why do slots eat through a budget so quickly?+
Most slot returns come from rare, large wins, so long stretches of small losses are normal. High-volatility slots need a much larger budget, or a much smaller stake, than table games with the same RTP.
Does the Martingale system reduce risk?+
No. It makes small wins more likely and big losses less frequent but much larger. The average result over many sessions is the same loss the house edge predicts.
What stake should I use for my budget?+
As a rule of thumb, around 1% to 2% of your session budget per bet on even-money table games, and less on slots, gives a reasonable chance of playing a few hundred rounds without running out.
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