Venue A (YES)vsVenue B (NO)
Prediction Market Arbitrage Calculator
Enter a YES price and a NO price -- from the same market, or matching contracts on two venues covering the same outcome -- to see whether they sum to under $1, the stake split that equalizes payout, and the guaranteed profit if one exists.
Real arbitrage: $15.46 guaranteed profit on $500.00 (3.09% return)
Buy 515.5 matched contracts of each side; exactly one side pays $1, guaranteeing the same profit regardless of outcome.
Combined cost (per $1 payout)
97.00¢
Guaranteed profit per $1 payout
3.00¢
Return on capital
3.09%
| Venue A (YES) | Venue B (NO) | |
|---|---|---|
| Price incl. fees | 45.00¢ | 52.00¢ |
| Stake | $231.96 | $268.04 |
| Matched contracts | 515.5 | 515.5 |
| Payout if this side wins | $515.46 | $515.46 |
How this is calculated
Combined cost = YES price + NO price (plus fees on each leg, if any). When that's under $1, buying one of each locks in the difference as profit, since exactly one side always pays $1. At 45¢ + 52¢ = 97¢, that's 3¢ of guaranteed profit per dollar of eventual payout -- a 3.09% return on the capital actually deployed.
The stake split divides your budget so the number of YES contracts bought equals the number of NO contracts bought -- matching payouts 1-for-1 regardless of which side wins. On a $100 budget at these prices, that's 103.09 contracts of each, costing $46.39 and $53.61 respectively.
The profit is only guaranteed if both legs actually settle the same way. Same-market YES/NO arbitrage carries no settlement risk (there's only one resolution). Cross-venue arbitrage does -- two platforms can define, source, or time the same real-world question differently, which is the real risk this trade carries even when the math above says it's riskless. Prediction markets involve risk of loss and may be restricted in some jurisdictions.
Frequently Asked Questions
Why does buying both YES and NO ever make sense?
Because YES and NO are complementary -- exactly one of them pays $1, always. If you can buy one contract of each for less than $1 combined, you've locked in the $1 payout for less than it's worth, and it doesn't matter which side wins. On the default 45¢ YES / 52¢ NO example, the pair costs 97¢ and pays $1 no matter what happens -- a guaranteed 3¢ per dollar of eventual payout.
Why is the stake split unequal in dollars?
The split isn't 50/50 in dollars -- it's equal in CONTRACTS. You need exactly one NO contract for every YES contract so that whichever side wins, you're holding exactly one winning $1 contract. Since YES and NO have different prices, matching contract-for-contract means unequal dollar amounts: on $100 of capital at 45¢/52¢, that's roughly $46.39 on YES and $53.61 on NO.
Why doesn't this show up all the time?
Because it's free money if it's real, and free money gets traded away fast. Market makers price both sides to protect their own margin (the vig), so the two sides of one market almost always sum to MORE than $1, not less -- see the implied-probability calculator's vig section. A true arbitrage usually only appears briefly, across two different venues that haven't caught up to each other yet, or in a very thin/newly listed market.
What's the catch with cross-venue arbitrage specifically?
Settlement risk. Buying YES on one venue and NO on another only guarantees a profit if both venues resolve the underlying question the SAME way, using the same rules, sources, and deadlines. Two venues can disagree on an ambiguous outcome, use different settlement sources, or have different resolution dates -- any of which can turn a 'guaranteed' arbitrage into a position where both legs lose, or where you're stuck holding an unresolved contract on one side after the other has already settled.
What does the no-arbitrage example show?
At YES 55¢ / NO 52¢, the combined cost is 107¢ -- over $1 -- so buying both sides here guarantees a LOSS of 7¢ per dollar of payout, not a profit. This is the far more common case: two overlapping quotes usually cost more together than the $1 they can ever pay out, because that gap is the market's margin.
SidebySideCalc's prediction-market calculators apply standard odds, probability, and bankroll-sizing math to the numbers you enter -- they are not trading advice. Prediction markets carry real risk of loss and may be restricted or unavailable in some jurisdictions; nothing here names or endorses a specific trading venue.