Unit sizing: how much one bet should be
A unit is the stake you treat as one normal bet, usually 1–2% of the money set aside for betting. Keep it small enough that a long losing run is an inconvenience, and scale it with your bankroll.
Updated September 27, 2026 · TrueEdge Academy
A unit is the amount you stake on one ordinary bet, and the common convention is 1% to 2% of your bankroll — the money set aside for betting and nothing else. With a $5,000 bankroll, one unit is $50 to $100. Every bet is then described in units rather than dollars, which does two jobs: it stops any single result from mattering much, and it lets you compare your record with someone betting ten times your size. This guide covers how to pick the number, when to change it, and how it connects to the Kelly criterion.
Why 1–2% and not 10%
Because losing streaks are longer than they feel like they should be. Even a bettor with a genuine edge wins barely more than half of their even-money bets, and over hundreds of bets a run of eight or ten straight losses is not bad luck, it is expected. The unit has to be sized for that run, not for an average week. Variance covers the statistics in depth; the example below is the short version.
- Chance of 8+ losses in a row somewhere in 500 bets
- about 63%
- Chance of 8+ in a row somewhere in 1,000 bets
- about 86%
- Chance of 10+ in a row somewhere in 1,000 bets
- about 39%
- 20 straight losses at 1% flat units
- −20% of bankroll
- 20 straight losses at 10% flat units
- the bankroll is gone after 10
Computed for independent bets that each win exactly 50% of the time. A small edge shortens these runs only slightly, and long-odds bets make them far longer.
Flat units vs proportional units
A flat unit stays the same dollar amount until you decide to change it. A proportional unit is always the same percentage of whatever the bankroll is now, so it shrinks after losses and grows after wins. Flat units are simpler and are how most people record their results. Proportional units protect you better, because a drawdown automatically cuts your stake — the same 20-bet losing run costs about 18% at 1% proportional, against 20% flat. The common compromise is to keep a flat unit and re-set it on a schedule, such as the first of each month, to 1% of the bankroll on that day.
- Start: bankroll $5,000
- unit $50
- Month 1 ends at $5,600
- unit becomes $56
- Month 2 ends at $4,900
- unit becomes $49
- 20 losses in a row, 1% proportional
- 5,000 × 0.99²⁰ = $4,089.55 left (−18.2%)
- 20 losses in a row, $50 flat
- $5,000 − $1,000 = $4,000 left (−20%)
Sizing down after losses feels like giving up. It is what keeps a bad month from turning into a bad year.
How units relate to Kelly
A unit is a fixed stake; Kelly gives a different stake for every bet, sized to its edge and its odds. The bankroll guide explains why almost everyone uses a fraction of Kelly, usually a quarter. The useful bridge is to express the Kelly stake in units: a strong edge at short odds might be 1.1 units, a small edge on a long shot 0.4. That keeps the discipline of units while letting the size follow the maths. Kelly's formula for the fraction of bankroll to bet is (b × p − q) ÷ b, where b is the decimal odds minus one, p the fair win probability and q = 1 − p.
- Bet A: fair 50%, price +110 (decimal 2.10)
- EV +5% per dollar
- Full Kelly: (1.10 × 0.50 − 0.50) ÷ 1.10
- 4.55% = $227.27
- Quarter Kelly
- 1.14% = $56.82, or 1.1 units
- Bet B: fair 25%, price +320 (decimal 4.20)
- EV +5% per dollar
- Full Kelly: (3.20 × 0.25 − 0.75) ÷ 3.20
- 1.56% = $78.13
- Quarter Kelly
- 0.39% = $19.53, or 0.4 units
Same edge, very different stakes. The long shot loses three times in four, so Kelly bets less on it — a flat 1-unit stake on both would over-bet B and under-bet A.
Where units don't apply
Units are for bets whose result you are exposed to. An arbitrage or a converted bonus bet is sized by its own hedge arithmetic, because both stakes are set by the prices, not by a unit; see how to convert bonus bets. What still applies is the ceiling: never have more in play at once than you could lose if a book voided one leg.
Doing it in TrueEdge
In Settings you enter your bankroll, a risk level (quarter, half or full Kelly) and a hard maximum per bet as a percentage of bankroll. The Positive EV screen then suggests a fractional-Kelly stake for each bet, never above that cap, and it is a suggestion rather than an instruction. The Bet Tracker shows your Bankroll — cash across the book balances you maintain plus stakes riding on open bets — which is the figure to re-set your unit from. The walkthrough explains each tile.
Frequently asked questions
- What is a unit in sports betting?
- Your standard stake for one ordinary bet, usually 1–2% of your bankroll. Records kept in units can be compared across bettors of any size.
- How much should one unit be?
- 1% of your bankroll is a sensible default, 2% at most for most people. At 1%, twenty straight losses cost about a fifth of the bankroll, which is survivable.
- Should I bet the same number of units on every bet?
- Not if you can estimate your edge. Fractional Kelly bets more on bigger edges and less on long shots; expressing that stake in units keeps it readable.
- When should I change my unit size?
- On a schedule, such as monthly, to the same percentage of your current bankroll. Resizing after every bet is proportional staking; never raising it after a loss is the rule that matters.