A 54% bettor at −110 is still behind after 100 bets 38% of the time.
01 · Units
Bet in units, not in moods
A bankroll is money set aside only for betting, sized so that losing all of it would not change your life. A unit is a fixed slice of it, commonly 1% to 2%. Every bet is sized in units, so a bad week costs a predictable number of units instead of whatever felt right at the time.
- Pick the bankroll once. Add to it on a schedule, never to chase a loss.
- Set the unit at 1% to 2%. Smaller if you bet many props or parlays.
- Re-size the unit monthly, not after every bet. Up when the bankroll grows, down when it shrinks.
- Record every bet in units. It is the only honest scorecard.
02 · Variance
Variance is bigger than it feels
Take a bettor with a genuine edge: a true 54% at −110, where break-even is 52.38%. Each bet is worth about $3.09 per $100. To be ahead after 100 bets they need 53 wins. Chance alone keeps them short of that surprisingly often.
| After | Wins needed | Chance behind |
|---|---|---|
| 100 bets | 53 | 38.1% |
| 250 bets | 131 | 28.4% |
| 500 bets | 262 | 22.3% |
| 1,000 bets | 524 | 14.8% |
Even after 1,000 bets, a real edge leaves about one chance in seven of being behind. That is why a month of results says very little about whether you are any good, and why closing-line value, which needs far fewer bets to read, is the better scorecard. Closing-line value explains it.
03 · How much to bet
How much of the bankroll an edge deserves
The Kelly criterion answers how much to stake for the fastest long-run growth: for a 54% bet at −110 it says 3.4% of the bankroll. Most serious bettors stake a quarter or a half of that, because full Kelly swings hard and assumes you know your true edge exactly. Nobody does. Kelly staking has the full working.
Bet it: $13.75 is quarter Kelly's 1.38% of $1,000.00 at −110.
Full stake 5.50% · fastest growth, only if your 55.0% is exactly rightPast 11.0% you shrink
- The price implies
- 52.4%
- Your edge over it
- +2.6 pts
- Full stake: (b × p − q) ÷ b
- 5.50%
- The stake you bet at a quarter
- $13.75
Before you bet
What this means for your next bet
- Size this bet in units from a bankroll you set aside in advance.
- Keep the unit at 1% to 2% of the bankroll, or smaller for props and parlays.
- Judge yourself by whether you beat the closing price, not by last week's results.
- Never raise a stake to chase a loss.
Questions3 questions
How much should I bet per game?
Most bettors use a unit of 1% to 2% of a dedicated bankroll per bet, and less on high-variance bets like props and parlays. The Kelly criterion gives an upper bound for a known edge; a quarter or half of it is the common choice.
What is a unit in sports betting?
A unit is a fixed fraction of your betting bankroll used as the standard bet size. Recording results in units makes them comparable across bankroll sizes.
How long does it take to know if I am a winning bettor?
Longer than most people expect. A bettor who truly wins 54% at −110 is still behind after 500 bets about 22% of the time. Closing-line value is a faster read than wins and losses.
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Research and education only. Results vary, and nothing here promises a profit. Every number from our own data names its sample and its dates; every worked example is the arithmetic of the prices shown.