Betting Unit Size & Bankroll Calculator
Set a betting unit from your bankroll and risk level, size a bet in units, and see how a losing streak would hit your bankroll with flat units versus percentage staking before you place it.
How it works
unit = bankroll × unit % · stake = units × unit · flat staking after k losses = bankroll − k × unit · percentage staking after k losses = bankroll × (1 − unit %)ᵏ · losses to halve = ln 0.5 ÷ ln(1 − unit %)
A unit is a fixed slice of a dedicated betting bankroll — money you can afford to lose entirely. Betting in units keeps every stake small relative to the bankroll so that the inevitable losing runs do not wipe it out; at -110 odds even a 55% winner is more likely than not to hit eight straight losses somewhere in 1,000 bets. Flat staking keeps the unit fixed; percentage staking recalculates it from the current bankroll, which shrinks stakes as you lose and can never reach zero. Units also make results comparable between bettors who stake different amounts.
Worked example
With a $1,000 bankroll and 2% units, one unit is $20.00 and a 1-unit bet stakes $20.00. Ten straight losses leave $800.00 with flat staking or $817.07 with percentage staking, and it would take about 34 straight losses to halve the bankroll at 2% per bet.
Sources: NCPG — Responsible gambling · Wikipedia — Kelly criterion
Frequently asked questions
What is a unit in sports betting?
A standard bet size, usually 1–2% of your bankroll. With $500 set aside, one unit is $5–10. Bettors report results in units so that "+12 units" means the same whatever their bankroll.
How much of my bankroll should I bet?
Most bankroll guides suggest 1–3% per bet, and up to about 5% only for very strong conviction. The Kelly criterion gives a maximum based on your edge, but most professionals bet a fraction of Kelly.
How long can a losing streak be?
Longer than you think. A bettor who wins 52% of even-money bets has roughly a 30% chance of a 10-loss streak somewhere in 1,000 bets, which is why small units matter.
Where can I get help with gambling?
If you are chasing losses, betting more than you planned or borrowing to bet, stop and talk to someone: 1-800-GAMBLER (US), GamCare (UK), Jugar Bien (Spain) or your local helpline. Deposit limits and self-exclusion tools are available at every licensed bookmaker.
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For information and entertainment only — not betting advice. Gambling carries a real risk of loss, odds and settlement rules vary by bookmaker and country, and betting is only for adults where it is legal. Never stake more than you can afford to lose; if gambling stops being fun, get free, confidential help (for example 1-800-GAMBLER in the US, GamCare or BeGambleAware in the UK, or your local helpline).