- Maths reviewed by Josh Miller
- Tested by Diana Westfield
A poker bankroll calculator answers “how many buy-ins do I need?” with your numbers instead of a forum rule. Say you win 4 big blinds per 100 hands at $0.25/$0.50 with a standard deviation of 90. A $1,000 bankroll is 20 buy-ins, and that comes with a 14% risk of going broke. For 5% risk you need about 30 buy-ins, and for 1% about 47. Free, with modes for cash games, MTTs and sit & gos.
Poker bankroll for cash games
The maths is the classic risk of ruin formula: e to the power of −2 × win rate × bankroll ÷ variance, everything in big blinds per 100 hands. The interesting part is what moves it. Win rate and standard deviation matter far more than the bankroll itself.
| Win rate (bb/100) | SD 80 | SD 100 | SD 140 (PLO) |
|---|---|---|---|
| 2 | 48 buy-ins | 75 buy-ins | 147 buy-ins |
| 4 | 24 buy-ins | 37 buy-ins | 73 buy-ins |
| 8 | 12 buy-ins | 19 buy-ins | 37 buy-ins |
That’s 100bb buy-ins for a 5% risk of ruin. Notice PLO. Same win rate, roughly double the bankroll. Your tracker shows your standard deviation; use that rather than a guess.
MTT and sit & go bankrolls
Tournaments are different. Most of the time you lose your buy-in, and now and then you win 50 or 100 of them. The CasinoCalcs calculator models a field where about 15% get paid and first takes roughly a fifth of the pool, and your ROI lifts your chance of every paid place.
A 15% ROI in 300-runner fields works out to a standard deviation of about 5 buy-ins per tournament. For a 5% risk of ruin, that’s around 280 buy-ins. People who play MTTs on 50 buy-ins aren’t wrong to try, they’re just taking a lot more risk than they think. Sit & gos are calmer: a 10% ROI needs about 38 buy-ins for the same 5%.
What the formula leaves out
Two big things. First, you don’t know your true win rate. 50,000 hands at 4 bb/100 with SD 90 has a 95% range of about ±8 bb/100. Plan with a conservative number. Second, real players move down after a bad run, which cuts risk of ruin a lot. The calculator assumes you don’t, so it’s a worst case.
To see how wild a sample can be, the poker variance calculator draws your possible graphs. Rakeback adds straight to your win rate, so check the rakeback calculator too. For the general formula, see the risk of ruin calculator.
Poker session tracker
The bankroll maths only works with honest numbers, so here’s a place to keep them. Log each session with what you bought in for, what you cashed out and how long you played. Add the big blind and hands and it works out your win rate in bb/100 as well as your hourly rate. Everything stays in this browser, with a CSV export for backups.
Once you have a few months logged, put your win rate and standard deviation into the poker variance calculator to see how much of it is luck.
A bankroll is money you can afford to lose. Keep it that way. BeGambleAware.org is free and confidential.