CobiaPolymarket vs Bovada, Pinnacle and DraftKings: Comparing Prices
Short answer: To compare Polymarket with a sportsbook, convert the sportsbook odds to an implied probability, remove the bookmaker margin (the vig), and put the result next to the Polymarket price in cents. If the two are within a cent or two, they agree. A bigger gap is a reason to check for stale quotes, thin liquidity or news, not proof of an edge.
Two different kinds of price
A sportsbook sets a line, adds a margin, and takes your bet. A Polymarket price comes from an order book where traders buy and sell shares from each other. The first has a margin built in. The second has none, but you pay the spread between the bid and ask. More on the structural differences is in prediction markets vs sportsbooks.
Step 1: convert the odds
For a negative American price, the implied probability is the price without the sign divided by that number plus 100. For a positive price, it is 100 divided by the price plus 100.
- -150 gives 150 / 250 = 60.0%.
- +130 gives 100 / 230 = 43.5%.
Step 2: remove the vig
Those two add to 103.5%. The extra 3.5 points are the margin. To remove it, divide each by the total: 60.0 / 103.5 = 58.0%, and 43.5 / 103.5 = 42.0%. Now they add to 100% and you can compare them with Polymarket. Our guide to the vig and devigging shows more methods.
Step 3: compare to the Polymarket ask
Use the price you would pay to buy, which is the best ask. If the devigged sportsbook figure is 58% and the Polymarket ask is 56 cents, the Polymarket side is two cents cheaper than the sportsbook view. If the ask is 61 cents, it is three cents dearer. Fees and the spread eat into small gaps, so a one cent difference is noise.
Which sportsbook to compare
Books are not equal. Pinnacle is known for low margins and for taking sharp action, so its line is a common reference. Bovada and DraftKings are retail books with wider margins and their own quirks. Aggregator sites that blend many books are not a single price you can bet. Use a named book. Cobia shows the Bovada, Pinnacle or DraftKings price, whichever matched the game, and says which one.
Why we freeze the line at fire time
Beside each Polymarket pick, Cobia stores the sportsbook price from the moment the pick fired and does not update it. A live line moves, and comparing an old pick with a new line tells you nothing. The frozen number is what a reader would have seen when the pick was posted. We never show a pre-game closing line for picks that fired after the game started, because nobody could have bet that price.
What a gap does and does not mean
- It can mean one venue is slow to react to injury news.
- It can mean a thin market with one large order moving the price.
- It can mean a different rule, such as overtime counted on one side and not the other.
- It does not mean the cheaper side wins. We measured our picks against the closing line and do not beat it on average.
A line that matches is a sanity check. A gap is a question. See the track record page for how our picks have actually graded.
Fees and limits
Polymarket trading can carry fees depending on the market, and sportsbooks can limit or close accounts that win. Both change over time, so check current terms. A price gap of two cents can vanish after a fee, and a sportsbook may cap your stake well below what the Polymarket book can absorb. Treat any comparison as a starting point and price in what it would really cost you to trade.
A full example
Take a tennis match. Bovada has Player A at -165 and Player B at +135. Converted, that is 62.3% and 42.6%, a total of 104.9%. Divide each by 1.049 and you get 59.4% and 40.6%. Polymarket shows Player A with an ask of 60 cents and Player B with an ask of 42 cents. Against the devigged book view, Player A costs about 0.6 cents more and Player B about 1.4 cents more. Both gaps are inside the spread, so the two venues agree and there is nothing to act on. A gap of five cents or more would be worth a second look at the quote age and the market rules.
Practical checks
- Confirm both markets cover the same bet, including overtime and retirement rules.
- Confirm the sportsbook quote is current. Quotes older than a couple of hours are unreliable.
- Use the ask, not the last trade.
- Remember sportsbook availability depends on your location. Cobia is analysis only and does not place bets for you.
Key takeaways
- Convert sportsbook odds to a probability and remove the vig before comparing.
- Compare with the Polymarket ask, not the last trade.
- A gap of a cent or two is noise.
- Freeze the line at the time of the pick when you compare it later.
- A price gap is a question to check, not proof of an edge.
FAQ
How do I compare Polymarket and sportsbook odds?
Convert the odds to an implied probability, remove the vig, and compare with the Polymarket best ask in cents.
Why are Polymarket prices different from Bovada?
Different traders, different margin and liquidity. Bovada builds a margin into the line, while Polymarket shows a plain quote with a bid and ask spread.
Which sportsbook is the best reference?
Pinnacle is a common reference because of its low margin. Bovada and DraftKings are useful as retail comparisons.
Does a cheaper Polymarket price mean a better bet?
Not by itself. It can reflect stale quotes, thin liquidity or different rules, and we do not claim our picks beat the closing line.
Why does Cobia freeze the Vegas line?
So the comparison shows what was available when the pick posted, rather than a line that has moved since.
Cobia grades every pick in public, losers included.
Units at 1 unit per pick, with the entry price beside the hit rate.
See the track record