Poker variance

Cash mode takes your win rate and standard deviation in bb/100, plus a hand count. A 5 bb/100 winner with a 90 bb/100 standard deviation expects 5,000 bb over 100,000 hands. The 95% range is about -690 bb to +10,690 bb. The chance of being down is about 4%.

MTT mode takes ROI, buy-in, and a tournament count. Type your standard deviation in buy-ins, or leave it blank and enter the field size.

Assumptions

Cash mode treats every 100 hands as one step on a normal curve. Expected win is the win rate times hands divided by 100. The swing is the standard deviation times the square root of hands divided by 100. The 95% range is that result plus or minus two swings. 90% uses 1.64 and 99% uses 2.58.

Tournaments use the same normal curve. A typed standard deviation is the per-tournament swing in buy-ins. If you leave it blank, the page estimates it from the field size: you either win the whole field or lose the buy-in, and your ROI sets how often you win. That estimate ignores rake, satellites, and real payout ladders.