How Prediction Market Odds Tracking Works

Q: Which prediction market has the better price?

It depends on the game and the moment. Kalshi, Polymarket, and Gemini each price independently based on their own traders, so the cheaper price for the same outcome can be on a different platform from one game to the next, or shift during the same game as trading continues. Scouting Ledger shows all three side by side so you can see which one currently has the better price for the specific game you're looking at.

Q: How do Kalshi and Polymarket differ?

Both are exchanges, not sportsbooks -- you're trading against other users, not against the house, and prices are set by ordinary buying and selling rather than a bookmaker's line. Each has its own separate pool of traders and its own order book, so the same game's price can differ between them, sometimes by a meaningful amount.

Q: How do prediction-market odds compare to sportsbook odds?

A sportsbook sets its own price and bakes in a fee (the vig) regardless of outcome. A prediction market's price isn't set by anyone -- it's wherever traders have collectively landed, updating continuously as people trade rather than on any one company's schedule. Scouting Ledger converts prediction-market prices into the same American-odds format sportsbooks use so the two are readable side by side.

What's a Prediction Market?

A traditional sportsbook sets a price (a spread or a moneyline) and takes bets against it. The number moves when the book decides to move it, and the book is always the other side of your bet.

A prediction market works differently. It's an exchange, more like a stock market than a sportsbook. Traders buy and sell "shares" that pay out $1 if an outcome happens (e.g. "Team A wins") and $0 if it doesn't. The price of that share, somewhere between $0 and $1, reflects what the crowd of traders currently thinks the odds are. If a share is trading at $0.60, the market is collectively pricing that outcome at roughly a 60% chance. Prices move continuously as people trade, not on any single company's schedule, and you're trading against other traders, not against the house.

Because each exchange has its own separate pool of traders and its own order book, the same game can trade at slightly different prices in different places at the same time — which is exactly what this app is built to surface.

What We Actually Track

Kalshi, Polymarket, and Gemini each run their own independent exchange with their own order book and their own traders. Their prices are formed separately — that's why they can (and often do) disagree with each other on the same game, and it's why comparing them side by side is useful. We connect to each of these three directly and track their real-time prices.

It's worth understanding, in general terms, that not every app you see prediction-market-style trading on is running its own separate order book. Some consumer apps offer access to an underlying exchange's market rather than operating an independent one of their own — in effect, the price you see on that app is the same price forming on the exchange behind it, just presented through a different interface. When that's the case, that app's price isn't a separate, independent data point the same way Kalshi, Polymarket, and Gemini are — it's a window into one of them.

We're describing a general industry pattern here, not making any claim about the specific business or legal relationship behind any particular app. If you're ever unsure whether an app you use is pricing independently, that's a good question to ask the app directly.

Alongside the three exchanges, we also track a traditional sportsbook reference line (labeled "Sportsbook" throughout the app) purely as a familiar comparison point — it's not an exchange, and it works the standard sportsbook way described above.

Frequently Asked Questions

Which prediction market has the better price?

It depends on the game and the moment — that's the reason to compare them rather than trust one by default. Kalshi, Polymarket, and Gemini each price independently based on their own traders, so the cheaper price for the same outcome can be on a different platform from one game to the next, or shift during the same game as trading continues. Scouting Ledger shows all three side by side so you can see which one currently has the better price for the specific game you're looking at.

How do Kalshi and Polymarket differ?

Both are exchanges, not sportsbooks — you're trading against other users, not against the house, and prices are set by ordinary buying and selling rather than a bookmaker's line. The practical difference for you: each has its own separate pool of traders and its own order book, so the same game's price can (and does) differ between them, sometimes by a meaningful amount. That's why Scouting Ledger tracks both independently rather than assuming they'll match.

How do prediction-market odds compare to sportsbook odds?

They're built differently, so it's not quite apples-to-apples. A sportsbook sets its own price and bakes in a fee (the "vig") regardless of outcome. A prediction market's price isn't set by anyone — it's wherever traders have collectively landed, updating continuously as people trade rather than on any one company's schedule. Scouting Ledger converts prediction-market prices into the same American-odds format sportsbooks use (see the Sportsbook column) so the two are at least readable side by side, even though what's driving each number is different.

Glossary — betting terms

The vocabulary every page here uses, written for someone who has never placed a bet.

Moneyline: The simplest market there is: pick the winner. The margin does not matter -- a one-point win pays the same as a forty-point win. Because the two teams are rarely evenly matched, the favorite pays less than you staked in profit and the underdog pays more.
Spread: The market evens out a mismatch by giving the underdog a head start in points. If a team is listed at -6.5, they have to win by seven or more for that side to pay; the other side at +6.5 pays if they win outright OR lose by six or fewer. The half-point exists so the result can never land exactly on the number.
Total: Nothing to do with who wins. The market posts a number for the combined final score and you take the side you think it lands on -- Over or Under. A 44.5 total pays the Over at 45 combined points and the Under at 44.
Anytime TD: A yes-or-no question about one player: do they score a touchdown at any point, in any way -- rushing, receiving, a fumble return, anything that counts as six points for them. Scoring twice pays the same as scoring once. This is the only player market this site tracks, and it is what the TD Scorers tab compares across venues.
Implied probability: Every price is a statement about how likely something is, just written in a trading format rather than a plain percentage. Converting it back gives you the chance the market is charging you for. It is always slightly higher than the market's real estimate, because the venue's cut is baked into the price -- which is why the two sides of a market add up to more than 100%.
Vig / juice: Two names for the same thing: the margin a venue takes for running the market. It is not a separate fee you see on a receipt -- it is already inside every number posted, which is why a coin-flip market never pays even money. Comparing the same claim across venues is really comparing how much of it each one is taking.
YES / NO contract: How an exchange expresses the same claim a sportsbook expresses as odds. You buy a contract for somewhere between 1c and 99c; if the event happens it settles at $1, and if it does not it settles at nothing. A 44c YES contract and a sportsbook's +127 are the same bet at roughly the same price, written two different ways.
Exchange vs Sportsbook: A sportsbook sets a price, takes the opposite side of your bet, and profits from its margin. An exchange matches you against another customer and charges a fee on the trade instead -- so its prices move with what people are actually willing to pay, and you can usually sell out of a position before the game ends. Kalshi and Gemini are exchanges; DraftKings and FanDuel are sportsbooks.

Glossary — labels on this site

OPPORTUNITY: Our label for the small, rare set of situations (Middles and Arbs) that look worth actually acting on — as opposed to ordinary market activity, which is just situational awareness. This is why the Live Market Feed page splits activity into a quiet "Market Activity" feed and a separate, prominent "Opportunities" feed.
WATCH: A price has been moving steadily in one direction over several readings — not necessarily actionable yet, but a trend worth keeping an eye on before it fully settles.
MIDDLE: A situation where two markets' spreads have drifted far enough apart that, in theory, both sides could win if the final result lands in the numeric gap between them ("the middle"). It's one of the two event types we consider a real Opportunity.
DIVERGENCE: Two markets disagree meaningfully on the same game's odds right now — one is pricing an outcome noticeably higher or lower than the other. That gap might mean one market has outdated information, or it might just be normal noise — either way, it's flagged so you can decide for yourself. In the feed, this event type shows up under the badge "EDGE" (below).
EDGE: The badge you'll actually see on a Divergence alert in the feed — "Edge" and "Divergence" refer to the same thing, a meaningful price gap between two markets on the same game.

How This Works