Your bankroll is a balance sheet
A bankroll is the money you have allocated specifically for betting, fully separated from rent, savings, retirement, and emergency funds. If a number on it would change a real-world decision - whether you eat out, whether you make a car payment, whether you sleep - the bankroll is too large.
The single most important property of a healthy bankroll is psychological detachment. You should be able to lose the entire balance without altering your life. That detachment is what lets you make mathematically correct decisions during drawdowns, when emotional bettors abandon process.
Units, not dollars
Most disciplined bettors size in units rather than dollars. A unit is typically 1% to 3% of bankroll, with 1% being the conservative default for full-time players and 2% common for recreational bettors with a documented edge.
Sizing in units forces you to scale risk with success and contract it after losses - automatic, mechanical, and emotion-free. A $1,000 bankroll at 1% units bets $10 per game. After a 20% drawdown to $800, units recalibrate to $8. After climbing to $1,200, they grow to $12. The system self-corrects without any willpower on your part.
- Conservative: 1% units. Survives extended drawdowns; slow growth.
- Standard: 2% units. The default for documented +EV bettors.
- Aggressive: 3%+ units. Faster growth, much higher risk of ruin in losing stretches.
- Recalibrate units monthly or after large swings (±20%), never after a single bet.
The Kelly criterion - and why almost nobody uses full Kelly
The Kelly criterion is the mathematically optimal bet size assuming you know your edge exactly. The formula for a single bet is: f = (bp − q) / b, where f is the fraction of bankroll to wager, b is the decimal odds minus 1, p is your true win probability, and q is 1 − p.
Example: at +100 (b = 1) with a true 55% win probability, full Kelly = (1 × 0.55 − 0.45) / 1 = 0.10 - a 10% stake. That is enormous. A 10-bet losing streak from full Kelly drops your bankroll to about 35% of its starting value.
Because real edges are estimated, not known, almost all serious bettors use fractional Kelly: quarter-Kelly (25% of the recommended fraction) or half-Kelly. Fractional Kelly sacrifices a small amount of theoretical long-term growth in exchange for dramatically lower variance and lower risk of ruin. If your edge estimate is wrong by more than 2x, full Kelly is negative-expectation.
Flat staking vs proportional staking
Flat staking risks the same dollar amount on every bet - typically 1 unit. It is the simplest system, the easiest to track, and the most resistant to bad edge estimates. It is what we recommend for nearly all recreational bettors.
Proportional staking (a Kelly variant) sizes each bet to a percentage of current bankroll. Wins compound faster; losses contract automatically. It requires confidence in your edge estimates, which is a confidence most bettors should not yet have.
Drawdowns are not failure - they are the contract
Even a bettor with a true 55% win rate at -110 will experience drawdowns of 10–20 units with high frequency over a season of normal play. Monte Carlo simulation of 1,000 bets at a 3% edge shows that a 30-unit drawdown happens in roughly half of all simulated bankroll histories. That is the variance you signed up for when you took +EV bets.
Risk of ruin is the probability that your bankroll hits zero before reaching some target. It is a function of edge, variance, and bet size. Doubling your unit size from 1% to 2% does not double risk of ruin - it can multiply it by 5x or more depending on your edge. This is why bet sizing is the most under-appreciated decision in betting.
Track everything, judge nothing in the short term
A serious bettor logs every wager: sport, market, side, stake, price taken, closing line, result, and notes. Without that record, you cannot compute CLV, true ROI, win rate by market, or any of the diagnostic signals that distinguish a slump from a broken process.
Track for at least 200–500 bets before drawing conclusions about your edge. Track CLV separately - it is your fastest indicator of whether you are actually beating the market or just getting lucky.
Frequently asked questions
What percentage of bankroll should I bet per game? Most disciplined bettors risk 1–2% of bankroll per bet, with 1% being the conservative standard. Anything above 5% is gambling regardless of edge.
What is the Kelly criterion in sports betting? A formula that computes the mathematically optimal stake given a known edge and price. In practice, most bettors use quarter or half Kelly to account for the fact that real edges are estimates.
How big should my starting sports betting bankroll be? Large enough that 1% of it is a stake you would not regret losing. For most recreational bettors, that is between $200 and $2,000.
How do I know when to increase my unit size? After a large, sustained bankroll growth (typically 20%+) over a meaningful sample (hundreds of bets), not after a single hot week. Recalibrate units, not stakes mid-stream.