What Is a Surebet in Betting and How to Calculate It
A surebet is an odds gap between bookmakers where betting on every outcome locks in a profit. Formula, worked example and 24 hours of Dozor scanner data.
A surebet (also called an arb, or arbitrage bet) is a set of bets on every outcome of one event, placed with different bookmakers, where the sum of the inverse odds is less than one. Whatever happens in the match, the payout on the winning bet exceeds the total amount staked. According to Dozor scanner data for September 6, 2026, such gaps appear roughly 500 times an hour across esports and prediction markets, but half of them last two seconds or less.
The surebet formula
For two outcomes with odds k₁ and k₂, a surebet exists if
1/k₁ + 1/k₂ < 1
For three outcomes (win, draw, loss), you add up three inverse odds. The smaller the sum, the higher the return: a surebet's ROI equals 1 / sum − 1.
Stakes are split in proportion to the inverse odds so that the payout is the same whatever the outcome:
stake on outcome i = bankroll × (1/kᵢ) / sum
Worked example
A CS2 match, “winner” market. Bookmaker A offers 2.10 on the first team, bookmaker B offers 2.05 on the second.
| Step | Calculation | Result |
|---|---|---|
| Inverse odds | 1/2.10 + 1/2.05 | 0.476 + 0.488 = 0.964 |
| Is there a surebet? | 0.964 < 1 | yes |
| ROI | 1/0.964 − 1 | 3.7% |
| Bankroll | 10,000 ₽ | |
| Stake with A | 10,000 × 0.476 / 0.964 | 4,940 ₽ |
| Stake with B | 10,000 × 0.488 / 0.964 | 5,060 ₽ |
| Payout if the first team wins | 4,940 × 2.10 | 10,374 ₽ |
| Payout if the second team wins | 5,060 × 2.05 | 10,373 ₽ |
About 373 ₽ profit whatever the outcome. That is a 3.7% surebet.
Where surebets come from
Bookmakers price an event independently, and their lines move at different speeds. Gaps arise for three reasons.
- Different views of the outcome. Analysts at two bookmakers see the chances differently, especially in tier-2 esports, where there are few public stats.
- Update lag. In live betting, one bookmaker has already reacted to something in the match and the other hasn't yet. These surebets last seconds.
- Different kinds of venues. Prediction markets such as Polymarket and Kalshi set prices through trading between participants, not by an analyst. Over the 24-hour sample, Polymarket was involved in 11% of all surebets Dozor found, most often paired with Duel, Winline and Pinnacle.
Which markets produce the most surebets
Breakdown by market type of 10,000 surebets Dozor recorded over 20 hours on September 5–6, 2026:
| Market | Share of surebets |
|---|---|
| Handicap | 33% |
| Winner | 25% |
| Total | 20% |
| Team totals | 8% |
| Round handicap | 4% |
| Total kills (Dota 2, LoL) | 3% |
| Other | 7% |
Handicaps and totals produce more surebets than the match result: there are many numeric lines, and books disagree on them more often.
How long a surebet lasts
This is the main constraint. In the same sample, 39% of surebets disappeared in two seconds or less, the median lifetime was 2.1 seconds, and 5% lasted longer than a minute. A detailed breakdown by market is in the article “How Long Does a Surebet Last? Data from 10,000 Surebets”.
The practical takeaway: hunting for surebets by hand, switching between bookmaker tabs, is pointless. By the time the second bet is placed, the odds have already changed.
Between which bookmakers
Over 24 hours, Dozor found surebets between 27 bookmakers and exchanges across 342 distinct pairs. The most frequent pairs: Betcity and Duel, Duel and Olimp, Duel and Marathon, Duel and Winline, BC.Game and Marathon. The general pattern: surebets form between books that get their lines from different providers. Brands on the same provider (for example, Fonbet, Pari and Bettery) don't produce surebets with each other, and the Dozor scanner doesn't show such pairs.
Risks the definitions leave out
- Account limiting. A bookmaker that notices surebet betting cuts your maximum stake to a token amount. This, not losing, is the main risk.
- Voided bets. A bookmaker is entitled to settle a bet placed at erroneous odds at odds of 1. The other leg of the surebet then remains an ordinary bet.
- Different settlement rules. Total rounds on a map and total rounds in the match are different markets. Books treat overtime, forfeits and replays differently.
- Fees and currency. On prediction markets the price is in dollars, and there's a platform fee and a spread. Calculate ROI after them.
- Execution time. The odds can move between the first and second bet. A 3% surebet turns into two ordinary bets.
How to find surebets
By hand: open 5–10 bookmakers, find the same event on all of them, compare the odds market by market, and repeat every few seconds. One pass takes minutes; a surebet lives for seconds.
With a scanner: the service reads every bookmaker's lines at once, matches events and shows only the pairs where the sum of inverse odds is below one, with the ROI, the stakes and the age of each price.
FAQ
Is a surebet guaranteed profit?
Mathematically, yes, if the odds are fixed. In practice, seconds pass between the calculation and the second bet: the odds change, the bet may be voided, the limit may be cut. This is low-margin work with operational risks, not a guarantee.
What ROI is normal?
According to Dozor data, the median is 3%, and three quarters of surebets are below 6%. Anything above 10% is worth checking for a line error.
Is it legal?
Betting on surebets is not prohibited by law. Bookmakers' rules allow them to limit accounts and void bets placed at erroneous odds.
Are there surebets in prematch, not just live?
Yes. They last longer, but they also appear less often. Live provides the bulk of the volume. More on the two modes on the Live surebets and Prematch surebets pages.
How is a surebet different from a value bet?
A value bet is a single bet at odds above fair value, so the risk of losing remains. A surebet covers every outcome.