Bankroll Calculator

How many buy-ins you actually need

The standard advice is "20 buy-ins for cash games, 50 for tournaments." Those numbers exist because they're easy to remember, not because they're correct. The actual number depends on your win rate, your standard deviation, your game type, and how much ruin risk you're willing to accept. For some players the correct answer is 15 buy-ins. For others it's 80. The calculator gives you the real number.

The model

The bankroll requirement is derived from the risk of ruin formula, inverted to solve for the bankroll B that produces a target ruin probability p:

B = -ln(p) * sd^2 / (2 * wr)

where wr is win rate in bb/100 and sd is standard deviation in bb/100. Converting BB to buy-ins: if you play 100bb stacks, divide B by 100. If you play 150bb stacks, divide by 150.

For tournaments, the equivalent calculation replaces the continuous formula with a Monte Carlo simulation over a fixed number of events, taking ROI and field size as inputs to generate the minimum buy-in count such that ruin probability falls below the target level.

Worked example: cash game

NL100 player, 3bb/100 win rate, 100bb/100 standard deviation, willing to accept 2% ruin risk.

B = -ln(0.02) * 100^2 / (2 * 3) = 3.912 * 10,000 / 6 = 6,520 bb

At NL100 with 100bb buy-ins: 65 buy-ins. That's $6,500 for the $100 game. Most players sitting NL100 have $1,000-$2,000 set aside. They're running 10-20x the appropriate ruin risk without knowing it.

Worked example: tournament

A player with 15% ROI playing $50 buy-in MTTs. Conservative 1% ruin target. The simulation output depends on field size, but a typical 1,000-player field at those parameters suggests needing roughly 60-80 buy-ins in reserve, or $3,000-$4,000, before running a serious schedule. If that player also has living expenses tied to their poker income, the professional multiplier pushes the number to 100-120 buy-ins.

What each output means

Required bankroll in buy-ins is the key number: how many full buy-ins you need in your poker account (or set aside for poker) to hit the selected ruin probability. Dollar amount translates buy-ins into the current stake. Conservative/standard/aggressive presets correspond to roughly 1%, 5%, and 10% ruin probabilities respectively. Move-up threshold answers the specific question: "how much do I need before taking a shot at the next level?" It runs the same calculation at the higher stake and shows you the bankroll number at which the move becomes defensible.

Where the model breaks

The formula assumes your win rate is known and constant. At typical sample sizes (50,000 hands for cash, 500 tournaments), win rates are uncertain by several bb/100 or several percentage points of ROI. The calculator takes your input at face value; if you're using a small-sample win rate estimate, add a margin of error.

The model also doesn't account for the psychological dimension of bankroll management. A player with a 40-buy-in bankroll who goes on a 10-buy-in downswing and moves down a stake is not following the model's assumptions. They're making a rational choice to manage risk by changing stake levels dynamically. The calculator is best used for setting initial bankroll minimums, not for mid-downswing decisions.

For professionals, the income-replacement angle matters too. If you're drawing living expenses from your bankroll, the effective drain on capital means your ruin probability is higher than a pure win-rate model suggests. The professional toggle in the calculator adds a monthly withdrawal assumption to the ruin calculation. This usually doubles the required bankroll compared to the recreational case.

For the variance side of the picture, use the variance calculator. For ruin probability in isolation, the risk of ruin calculator gives you more granular control over the inputs. The bankroll tool is the practical synthesis of both.

Advanced: stake ladder planning

The most useful application of the bankroll calculator is not finding the floor for your current game. It's plotting a path from where you are to where you want to be. A player grinding NL25 with aspirations to reach NL200 faces four consecutive move-up decisions, each requiring a different bankroll threshold. The stake ladder output shows all four numbers at once, along with how long it takes to reach each one at your current win rate. That projection is optimistic by definition (it assumes the win rate holds at every stake), but it converts an abstract goal into a concrete monthly savings target.