Craps Session Simulator

A craps session is a distribution, not a promise

Craps players rarely ask only one question. They usually want to know whether a bankroll is large enough for a planned session, how often they are likely to finish ahead, how violent the swings might feel along the way, and how often a reasonable-looking plan still ends in a bust before the night is over. This simulator is built for that practical set of questions. Instead of giving a single deterministic answer, it repeats the same betting plan many times and summarizes the spread of outcomes. That makes it useful for comparing calm bets with wild ones, short sessions with long ones, and comfortable bankrolls with fragile bankrolls.

The key idea is simple: the average result matters, but the path matters too. A bet can have a smaller house edge and still produce plenty of losing sessions if your buy-in is small relative to the stake size or if you plan to resolve the bet many times. Likewise, a longshot can occasionally post a dramatic win while still carrying a punishing risk of ruin. Seeing those tradeoffs side by side is more informative than hearing that one bet is good or bad in the abstract. The table summary, the ruin estimate, and the sample session trajectory work together to show what a flat-betting plan can feel like in actual play.

What each input means at a real craps table

Bet Type chooses the wager that will be resolved over and over in the simulation. Pass Line and Come are treated as pass-style bets, which usually means lower volatility than the more aggressive proposition bets. Don't Pass and Don't Come behave like the dark side of the table. Place bets win when their target number appears before a seven. Field resolves in a single roll. Hardways, Any Craps, and Any 7 are much more volatile because they pay more when they hit and lose more often while waiting for that hit. If your real casino plan uses a completely different mix of bets, think of this tool as a clean baseline for comparing volatility, not as a full reproduction of every layout detail.

Starting Bankroll is the money available to survive the session. In the simulation, it is the amount you begin with before the first resolution. It is not your lifetime gambling budget, not your ATM limit, and not the amount you are willing to reload later. If the bankroll falls below the stake size, that session stops early because you can no longer place the same flat bet. That rule is what makes risk of ruin meaningful here: a session can fail before you reach your planned number of resolutions.

Bet Size per Resolution is the flat amount risked each time the chosen bet is resolved. Think of it as your base unit. If you are testing whether a $15 Pass Line habit feels comfortable with a $300 buy-in, enter 15. If you are evaluating a more dangerous idea like repeated $15 Any 7 bets, the same stake tells a very different story because the payout structure and hit frequency are different. This is why stake size should always be considered relative to bankroll, not on its own.

Rounds per Session means resolved bets, not literal dice throws. A Pass Line or Don't Pass resolution can include a come-out roll and then several additional rolls before the bet wins or loses. A Place 6 bet can sit on the table through multiple rolls until a 6 or 7 appears. So if you enter 120 rounds, you are asking the simulator to complete up to 120 resolved bets of the selected type, stopping early if the bankroll runs out first.

Sessions to Simulate controls the stability of the estimate, not the rules of craps. More simulated sessions reduce noise in the averages and percentages because the Monte Carlo sample gets larger. They do not improve the expected value of the bet and they do not represent something you personally must play. If two runs with 200 sessions look noticeably different, that is normal Monte Carlo variation. If two runs with 5,000 sessions are still very different, then the bet itself is highly volatile.

• Use the bankroll input for the amount dedicated to this one session.
• Use the stake input for one flat wager size, not a progression system.
• Use rounds per session for how many resolved bets you hope to complete.
• Use sessions to simulate for estimate quality; larger values smooth randomness.

What the simulator is actually doing

Behind the form, the page runs a Monte Carlo experiment. One simulated session starts with the bankroll you entered. For each planned round, the code resolves the chosen bet according to that bet's payout rule. Pass-style bets use a come-out phase and point cycle. Don't Pass-style bets use the opposite win condition and reroll a 12 on the come-out to mimic the push handling in this simplified model. Place bets stay up until the selected number or a seven appears. Hardways require the target total to arrive as a double before a seven or an easy version of that number. After each resolution, the bankroll is updated and the session either continues or ends if the bankroll can no longer cover the next stake.

That process is repeated for the number of sessions you request, then the simulator summarizes the full distribution. The average final bankroll tells you where the center of the distribution landed. The average profit or loss shows the mean change from the original buy-in. The standard deviation measures how spread out the session outcomes were. Profit rate and risk of ruin are often the most intuitive figures because they answer plain-language questions: how often did this plan finish ahead, and how often did it go broke?

Even though this page uses repeated simulation rather than one closed-form formula, it is still helpful to keep the broad math in mind. At a high level, the session result depends on several inputs at once:

In practical craps terms, those inputs are the bet rule, bankroll, stake size, number of resolutions, and random dice outcomes. When a model combines multiple influences, it often behaves like a weighted sum of components:

For a gambling session, the equivalent idea is that each resolution contributes another push upward or downward to the bankroll path. A useful rule of thumb is that the expected final bankroll changes roughly with the number of resolutions, while the spread of outcomes tends to grow with the square root of the number of resolutions:

That is why longer sessions can feel dramatically rougher even when the average expected loss per bet stays modest. More action gives the house edge more time to work, and variance has more opportunities to push the bankroll into a hole before luck has a chance to recover.

Worked example: a $300 flat-betting plan

Suppose you begin with a $300 bankroll, risk $15 per resolved bet, and plan for up to 120 resolutions. If you simulate 1,000 sessions on the Pass Line, the average final bankroll will usually come in below $300 because the Pass Line still carries a house edge. But the average alone is not the whole story. Many sessions will finish above the starting amount, many will finish below, and some will end before all 120 planned resolutions because a bad sequence drains the bankroll under the $15 table unit.

Now change only the bet type while holding the bankroll, stake, and round count constant. A Field bet usually creates faster short-term swings because it resolves every roll and has a higher edge than Pass Line. Any 7 or a hardway can create an even more dramatic profile: the occasional big hit pushes the best-session number upward, but the standard deviation and ruin risk usually jump as well because long losing stretches are common. This is the practical value of the simulator. You can test whether the excitement of a higher-payout bet is worth the much larger chance that your buy-in disappears before the session length you wanted.

The sample trajectory shown below the main results is especially helpful in this example. It is not an average path; it is the first simulated run. That means it can look surprisingly good or surprisingly awful. Treat it the same way you would treat one real night at the casino: interesting, memorable, but not enough by itself to evaluate a betting plan. The full summary matters more because it tells you how that kind of path behaves over many repeated sessions.

How to read the results without fooling yourself

Avg Final Bankroll and Avg Profit / Loss are the center of the distribution. If the average final bankroll is close to your starting amount, that does not automatically mean the ride is comfortable. You could still have a plan that alternates between nice wins and ugly busts. That is why the next figures matter. Std Dev of Change tells you how wide the session outcomes spread around the average. Higher standard deviation means a more dramatic session, not a better one.

Chance of Profit answers the emotional question many players really care about: how often did I leave up money? In a negative-expectation game, this number can still be substantial for short sessions because luck dominates in the short run. Chance of Breaking Even is usually small for many bet types because exact returns to the starting bankroll become less common as the number of resolutions grows. Risk of Ruin is the operational warning light. It tells you how frequently the bankroll hit zero before the session ended. If that value is uncomfortably high, the plan may be too aggressive even if the chance of profit still looks tempting.

Best Session and Worst Session show the outer edges observed in the simulated sample, not hard mathematical limits. They help illustrate how extreme the swings can become in a realistic batch of sessions. Avg Rounds Completed is easy to overlook, but it is one of the most useful numbers on the page. If it is far below the round count you entered, then many sessions are ending early because the bankroll cannot support the plan. That is strong evidence that the stake is too large, the session is too long, or the chosen bet is too volatile for the buy-in.

Use the output comparatively. Keep all inputs fixed except one, rerun the simulator, and ask a narrow question such as: what happens if I raise the bankroll from $300 to $450, or if I keep the bankroll at $300 but cut the stake from $15 to $10? One-variable comparisons are where this tool is most reliable. They reveal whether a change mainly reduces ruin risk, mainly reduces spread, or mainly shifts the odds of finishing ahead.

Assumptions and limitations

This page models flat betting. It does not add free odds, lay odds, pressing, regressions, table hopping, hedging combinations, commissions, or changes in behavior after wins and losses. Come and Don't Come are approximated with pass-like and don't-pass-like logic rather than a full multi-bet table state. Place bets are treated as staying up until they win or seven out. Those choices make the simulator fast and useful for comparing session risk, but they also mean it is not a perfect diary of every possible casino strategy.

The simulator is best used as a planning and intuition tool. If a low-volatility bet still shows a bust rate that makes you uneasy, that is valuable information. If a longshot bet shows a dazzling best session but a brutal ruin rate, that is also valuable information. The point is not to predict the exact result of your next trip. The point is to test whether the relationship among bankroll, stake size, and session length is reasonable before real money hits the felt.