US edition. Work out how many buy-ins your bankroll needs from your win rate, swings and risk of ruin. Free, no account, with the formula and a worked example.
What does this result mean?
A poker bankroll calculator estimates how many buy-ins you need before normal variance has an acceptable chance of wiping out your roll. The answer depends on three inputs: your expected win rate, the standard deviation of your results and the risk of ruin you are prepared to accept. A stronger edge reduces the required bankroll, while larger swings or a lower risk target increase it. The result is a planning threshold, not a promise that a downswing will stop at that number. Use a conservative win rate and a realistic standard deviation from your own sample, then compare the result with the buy-ins you actually hold. If your bankroll is below the estimate, the practical options are to drop stakes, build the roll or take a tightly ring-fenced shot with a fixed stop point.
4
90
5%
30.3 buy-ins
Buy-ins needed
3,033.2
Bankroll (big blinds)
A bankroll is measured in buy-ins, not cash. The more your results swing (standard deviation) and the thinner your edge (win rate), the more buy-ins you need to ride out variance without going broke. The formula is bankroll in big blinds equals minus S squared times the natural log of your target risk, divided by twice your win rate.
Example
A 4 BB/100 winner with a 90 BB/100 standard deviation needs roughly 30 buy-ins to keep risk of ruin near 5 percent. At 20 buy-ins the risk of ruin is closer to 14 percent. Halve the edge to 2 BB/100 with a 100 BB/100 standard deviation and the 5 percent bankroll rises to about 75 buy-ins.
Estimates for study and planning only, not a profit promise. Overshove tracks your real sample so these inputs come from your own data.
What does this calculator compute?
The calculator uses win rate, standard deviation and acceptable risk of ruin to estimate how many buy-ins a cash bankroll needs. A higher edge lowers the required roll; a higher swing rate or lower risk tolerance raises it.
When should the result change your decision?
Use the result before moving up, taking a shot or rebuilding after a downswing. If the required buy-ins are above the roll you actually have, the clean move is to reduce the stake or ring-fence the shot.
How to use the answer responsibly
Treat the calculator as a planning tool, not a verdict on one session. A live poker input is usually an estimate: your win rate is noisy, your standard deviation changes by game type, and your future volume rarely matches the clean number you type into a form. The useful habit is to save the assumptions beside the result so you know what would need to change before the decision changes.
If the result pushes against what you wanted to do, do not smooth the inputs until the answer feels nicer. Make the conservative version first, using a lower win rate, a higher swing rate or fewer weekly hours. Then run the optimistic version. The space between those answers is the real decision area: where a shot needs a stop rule, where a move up needs more buy-ins, or where a good-looking hourly still needs a bigger sample.
Overshove calculators become more useful when the inputs come from your own logged sessions. Rake, tips, travel, hours, stake mix and session length all change the number. A generic benchmark can teach the shape of the problem, but a clean personal log gives the number you should actually act on.
Questions
How many buy-ins do I need?
It depends on your win rate and swings, but a common range for live cash is 25 to 40 buy-ins. Thinner edges and bigger swings push the number up; size it for a risk of ruin you can accept.
Does a bigger win rate mean fewer buy-ins?
Yes. A larger edge and a smaller standard deviation both lower the buy-ins needed, because variance has less room to bust you before the edge plays out.
What formula does this use?
Bankroll in big blinds equals minus standard deviation squared, times the natural log of your target risk, divided by twice your win rate. That is the risk of ruin formula rearranged to solve for the bankroll.
Does this work for gambling other than poker?
The maths applies to any repeated bet where you have a measurable edge and a measurable standard deviation, so it holds for advantage play and trading as well. It does not apply to negative-expectation gambling: with no edge, no bankroll size prevents eventual ruin, it only delays it.