What does this result mean?
If the interval crosses zero, the sample does not clearly distinguish a positive win rate from a negative one under this model.
BB per 100 confidence calculator
Updated October 2026 · by Tom Howcroft
Put a normal-model interval around an observed win rate. Free, no account. See the formula, assumptions and editable inputs.
5
90
100,000
-0.6
Approximate 95% low (BB/100)
10.6
Approximate 95% high (BB/100)
2.8
Standard error (BB/100)
Example
The example inputs below are hypothetical. Change them to inspect your own study scenario. Hold the observed rate and SD fixed while increasing the hand count to see the interval narrow.
Estimates for study and planning only, not a profit promise. Overshove tracks your real sample so these inputs come from your own data.
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
What formula does this tool use?
SE = 100-hand block SD / square root(hands / 100). The approximate 95% interval is observed BB/100 plus or minus 1.95996398454 × SE. Assumes stable independent blocks and known SD; estimated SD and heavy tails add uncertainty.
Is this tool free and does it require an account?
It runs in your browser for free with no account. The result is a study calculation under the stated assumptions, not a recommendation to play or a promise of winnings.