Stop guessing how many buy-ins you need. This calculator uses risk-of-ruin math with your actual win rate — not a one-size-fits-all rule of thumb.
Bankroll you need
$3,835
at $1/$2 · 5% risk of ruin
In buy-ins (100bb)
19.2
1,917 big blinds
Your current roll covers
25 buy-ins
Risk of ruin at current roll
2.0%
You're properly rolled for these stakes with 5.8 buy-ins of cushion. Consider taking a shot at the next stake once you clear its requirement too.
1% risk of ruin29 buy-ins · $5,895
2% risk of ruin25 buy-ins · $5,007
5% risk of ruin19 buy-ins · $3,835
10% risk of ruin15 buy-ins · $2,947
20% risk of ruin10 buy-ins · $2,060
The buy-ins you need scale with your variance and shrink with your win rate. That's why blanket advice like "30 buy-ins for cash games" is dangerous: a 6 bb/100 crusher and a 1.5 bb/100 grinder at the same stakes need wildly different rolls. The formula this tool uses — BR = (σ² / 2·wr) · ln(1/risk) — comes from classic gambler's-ruin mathematics and is the same model used by professional backers.
Two honest caveats. First, the model assumes your win rate estimate is correct — most players overestimate theirs, which silently doubles their real risk. Second, it assumes you never move down in stakes; being willing to drop down during a downswing is the single most powerful bankroll protection there is. Try the variance calculator to see what those downswings actually look like.
It depends on your win rate and variance, not a fixed rule. A strong winner (5+ bb/100) at a 80 bb/100 standard deviation needs roughly 20 buy-ins for a 5% risk of ruin, while a marginal 1–2 bb/100 winner needs 75+ buy-ins for the same safety. The common '20–30 buy-ins' advice assumes a solid win rate.
The classic risk-of-ruin model for a player with a normal profit distribution: required bankroll = (variance ÷ (2 × win rate)) × ln(1 ÷ acceptable risk). It assumes you keep playing the same stakes and never move down — moving down during downswings reduces the requirement substantially.
5% is the standard for players who can redeposit or rebuild from income. If your bankroll is your livelihood and can't be replaced, use 1% or lower. If you can reload easily and are taking a shot, 10% is defensible.
The same math applies but tournament variance is far higher — standard deviations of 5–7 buy-ins per tournament are common, which translates to bankroll requirements of 100–300+ buy-ins depending on field size and ROI. Enter your ROI and standard deviation in per-tournament units instead of bb/100.
Stacker calculates your real win rate, standard deviation, and bankroll automatically from your sessions — the numbers this calculator asks you to guess.