Betting Bankroll Management Calculator

Manage your betting bankroll and size every bet like a pro: Kelly criterion and fractional Kelly stakes, unit sizing with losing-streak risk, expected value, odds conversion and parlay payouts. Free, private and no sign-up.

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What bankroll management actually does

Bankroll management is the set of rules that decides how much you stake, not what you bet on. A bettor with a real 3% edge can still go broke betting 20% a game; a bettor with no edge loses slower and more predictably with 1% units. The goal is to survive variance long enough for your edge, if you have one, to show up.

Three numbers drive everything on this page: your bankroll, the price you can get, and your honest estimate of the true probability. The gap between the true probability and the break-even probability implied by the odds is your edge.

Kelly criterion and fractional Kelly

The Kelly formula, f* = (b·p − q) / b, gives the fraction of bankroll that maximises long-run growth. Here b is the net decimal odds (decimal − 1), p is your win probability and q = 1 − p. Kelly never bets when the edge is zero or negative, and it bets more as the edge grows or the price shortens.

Notice how small the numbers are. At -110 with a 55% win rate, which is an excellent long-run record, full Kelly is under 6% and quarter Kelly is about 1.4%. If someone recommends 10% plays, they are assuming an edge almost nobody has.

Why most bettors use ¼ to ½ Kelly

Kelly assumes your probability is exact. If you think you win 55% but really win 53%, full Kelly over-bets and growth collapses. Betting half Kelly gives up only about a quarter of the theoretical growth while roughly halving swings, and quarter Kelly is safer still. That is why the calculator defaults to quarter Kelly.

For a deeper walkthrough see the Kelly criterion calculator and our Kelly guide.

Unit sizing and losing streaks

Flat units are the simplest system: pick a percentage (usually 1–2%), bet one unit on standard plays, and re-size on a schedule. The table shows how many straight losses it takes to cut a $1,000 bankroll in half with flat bets, and how likely that streak is over 1,000 bets at a 53% win rate.

Even a winning bettor will see 8–10 game losing streaks over a season. Units small enough to absorb those streaks are what keep you in the game.

Expected value: the only reason to bet

EV is what a bet is worth on average: probability × profit if it wins, minus probability × stake if it loses. A -110 bet you win 50% of the time is −4.5% EV; at 55% it is +5%. Kelly sizing only makes sense on +EV bets. Use the EV calculator or find live +EV prices on the +EV finder.

Odds formats and implied probability

Every price implies a break-even probability: -110 is 52.38%, +150 is 40%, 2.50 decimal is 40%, 5/2 fractional is 28.57%. Two-sided markets add up to more than 100%. The excess is the vig. Convert prices with the odds converter and strip the vig with the implied probability calculator.

Parlays and your bankroll

Parlays multiply both the payout and the house edge. Three -110 legs pay about +596, which needs a 14.4% hit rate to break even, while three true coin-flip legs hit only 12.5% of the time. If you play them, size parlays as fractions of a unit. Check payouts with the parlay calculator.

Bankroll rules that hold up

• Separate betting money from living money, and never top it up to chase losses.
• Stake 1–2% per standard play, or ¼–½ Kelly if you have a measured edge.
• Shop lines: a half-point or 10 cents on the price is often the whole edge. Use the odds board.
• Track every bet in units and review closing line value, not just wins (see CLV).
• Set a stop: if the bankroll falls 50%, pause and re-evaluate before betting again.