Arbitrage Calculator (2-book)
Back to the calculator. · Related: Implied probability, Kelly, No-vig odds.
Overround
Arb exists?
Stake on A
Stake on B
Profit if A wins
Profit if B wins
Guaranteed profit
ROI
Unspent bankroll
Surebet condition: sum of inverted odds < 1. For 2-way: 1/oA + 1/oB < 1. For 1X2: 1/oH + 1/oD + 1/oA < 1. Stakes are allocated proportionally to 1/odds so payouts are as equal as rounding and caps allow.
What is an arbitrage bet (surebet)?
An arbitrage or surebet appears when different bookmakers disagree enough that combining their best prices makes the market’s overround drop below 100%.
In a 2-way market this happens when 1/oA + 1/oB < 1. In 1X2, 1/oH + 1/oD + 1/oA < 1.
Stake sizing & profit
The calculator allocates stakes proportionally to the inverse odds so that payouts are as equal as rounding (and any caps) allow. Guaranteed profit is the minimum of per-outcome profits, and ROI is profit divided by total stakes.
Worked example (2-way)
Odds 2.10 and 2.10 → overround ≈ 1/2.10 + 1/2.10 = 0.9524 (95.24%). With €1000 bankroll and €5 rounding the tool proposes stakes so that both outcomes return ~equal and lock a profit.
Notes
- Rounding down to your step may leave small unspent bankroll to avoid overspend.
- Per-book caps are respected; if a side is capped, remaining bankroll is redistributed to others.
- Consider limits, delays, void rules and correlated markets — a mathematical surebet isn’t always practically risk-free.
How to use this calculator
- Select Market: 2-way or 1X2.
- Choose Odds format and type odds in that format (Decimal / American / Fractional).
- Set Bankroll to allocate and Stake rounding (e.g. €5).
- Optionally set max stakes (caps) per book/outcome.
- See Overround, whether an Arb exists, suggested stakes, per-outcome profit, guaranteed profit (min of outcomes), ROI and any unspent bankroll.
Related concepts: remove margin with No-vig odds, convert formats with Odds formats, and value-bet with this guide.