What a betting unit is and how to size one
A betting unit is a fixed slice of your bankroll used to size every stake. What it is, why it helps, how big to make it, and what a losing run costs in units.
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A betting unit is the amount you treat as one standard stake, set as a small, fixed slice of the money you have put aside for betting. Most people who use them make one unit 1% to 2% of that bankroll. The point is not the number. It is that every stake is decided before the bet, not by how the last one went.
Why bother with units
Three reasons.
It caps the damage. If one unit is 1% of your bankroll, no single loss can hurt much, and you have to be wrong many times in a row before the bankroll is in trouble.
It makes your record honest. Writing results as "plus 6 units from 40 bets" means the same at any stake size, and it stops one big bet from hiding how the rest went.
It takes the mood out of it. A unit set in advance is a decision you made calmly. Doubling up after a loss is a decision made in a hurry.
How big to make it
Start with the bankroll, and only money you could lose entirely without it mattering. Then pick the slice.
Say you set aside 500. At 1%, a unit is 5. At 2%, it is 10. Here is what a bad run does at 1%:
- Ten losses in a row cost 10 units, a tenth of the bankroll.
- Twenty in a row cost a fifth.
- If you recalculate the unit as 1% of whatever is left after each bet, twenty losses cost about 18.2%, because each stake shrinks as the bankroll does.
Twenty losses in a row sounds absurd until you bet at long prices. It happens more often than people expect, which we work through in how long a losing run can honestly last.
Fixed units or sized to the edge
The simplest version is one unit on everything. The alternative is to stake more when you think the edge is bigger, which is what the Kelly criterion formalises (from John Kelly's 1956 paper). It grows a bankroll fastest in theory, but only if your probabilities are right, and they never quite are. The trade-offs are in flat stakes versus percentage stakes and what Kelly actually tells you to do.
What this does not tell you
A unit system does not make a losing approach win. It only makes losses slower and easier to see. It also does not tell you what your edge is, if you have one. And if betting has stopped being money you can afford to lose, units are not the answer; BeGambleAware has free, confidential help.
18+. Bet only what you can afford to lose.
Common questions
What is a unit in betting?
A unit is a fixed amount you use as your standard stake, usually set as a small slice of the money you have put aside for betting. Bets are then described and sized in units instead of in money.
How big should a betting unit be?
Small. A common convention is 1% to 2% of a bankroll you can afford to lose entirely. At 1%, twenty losses in a row cost a fifth of the bankroll, which is painful but survivable.
Why record results in units instead of money?
Because it makes records comparable. A profit of 10 units means the same thing whether your unit is 2 pounds or 200, and it stops a bigger stake on one bet from hiding how the rest went.