Polymarket vs Kalshi NFL: Cheapest on 61 of 105 Lines
A pre-kickoff snapshot of 105 NFL lines on three venues, and what fee formulas and vig do to the price a buyer actually pays.
Published 2026-10-23 · Data as of 2026-10-23 · Market & data intelligence · Educational, not advice.
On October 23, ahead of the weekend's games, Delta Arc compared 105 NFL lines on Kalshi, Polymarket and DraftKings, each converted to the all-in cost of a $1 payout. Polymarket was cheapest on 61 lines, DraftKings on 28 and Kalshi on 16. Median gaps were about a cent or two, and fee design and vig shape which venue lands where. A Monday follow-up will score these prices against the results.
At 13:57 UTC on October 23, Delta Arc's BM Dash took a snapshot of 105 NFL lines across 14 upcoming games, priced on three venues: Kalshi, Polymarket and DraftKings. None of it is a live reading. It shows what a buyer would have paid at one moment, at the best ask. The snapshot does not capture order size or available depth.
What price means in this comparison
A comparison across venues only works if every number measures the same thing. Delta Arc put each price on one scale: the all-in cost of a $1 payout for a buyer. Lower is cheaper. That matters because the number on the screen and the number you actually pay are not always the same.
On Kalshi, the all-in price is the best ask plus the taker fee. Kalshi's fee schedule sets that fee at 0.07 × contracts × price × (1 − price), rounded up to the next cent. Per Polymarket's documentation, sports takers there pay 0.05 × shares × price × (1 − price). The Polymarket prices in the snapshot include that fee.
Look at the shape of both formulas. The price × (1 − price) term is largest when a contract trades near the middle of its range and shrinks toward either end. So the fee is heaviest on close games and lightest on lopsided ones. Kalshi's rounding up to the next cent adds a little more on small orders.
DraftKings works differently. Kalshi and Polymarket are exchanges. Every contract has a buyer and a seller, and the venue matches them and takes a fee without ever holding the other side. DraftKings is a sportsbook. It sets its own odds, takes the other side of every bet and builds its margin, the vig, into the price. The DraftKings figures here are the implied probability of the posted American odds, vig included, from ESPN's odds feed.
Which venue was cheapest, line by line
Out of the 105 lines, Delta Arc found Polymarket cheapest on 61, DraftKings on 28 and Kalshi on 16.
The head-to-head between the two exchanges was more lopsided. On the 75 lines priced on both, Polymarket was cheaper than Kalshi on 71, with a median gap of 1.3 cents per $1 of payout. One structural difference is easy to see: Polymarket's sports fee uses 0.05 where Kalshi's uses 0.07. The other factor is the order book itself, meaning who was offering contracts at what price at 13:57 UTC. The snapshot shows the result. It doesn't show how much came from each factor.
Kalshi and DraftKings were closer. Kalshi was cheaper for the same outcome on 28 of 74 comparable lines. An exchange with a fee and a sportsbook with vig both charge for access. They just collect the charge in different places.
How wide the gaps were by market type
A cent per $1 of payout equals one percentage point of implied probability, so these gaps are easy to read. Delta Arc measured the median distance between the cheapest and most expensive venue for each type of line:
- Moneylines: 1.6 cents per $1 of payout, across 28 lines.
- Point spreads: 1.3 cents, across 34 lines.
- Totals: 0.8 cents, across 43 lines.
These are small numbers, but they add up. On a contract that pays $1, a cent or two is a real part of the cost. The snapshot doesn't say why totals had the smallest gaps of the three, and we won't guess.
The widest spreads in the snapshot
Medians hide the extremes. At 13:57 UTC on October 23, a few lines stood well apart:
- Under 32.5, Dallas at Philadelphia: 14.4 cents on Polymarket, 18.0 cents on Kalshi.
- Under 47.5, Carolina at Green Bay: 53.5 cents on DraftKings, 57.0 cents on Kalshi.
- NYG +9.5, New York Giants at Houston: 45.8 cents on Polymarket, 49.0 cents on Kalshi.
The first example deserves a second look. On a low-priced contract, a few cents is a large fraction of the whole price. The same gap on a contract near 50 cents is a much smaller fraction. It is the same outcome on each venue, with different counterparties and a different cost.
What the highest-priced contracts imply
Delta Arc's numbers show the weekend's biggest moneyline favorites on Kalshi. As of the 13:57 UTC snapshot on October 23, Houston to win against the Giants cost 82.0 cents all-in, Minnesota against Indianapolis 74.0 cents, and Denver at Arizona 69.0 cents.
One caution when reading them: these are all-in costs, so the fee is already inside the number. That puts each figure slightly above the bare market price, which means the probability the market itself implies is a little lower than 82, 74 and 69 percent. For a buyer, the fee makes every outcome cost a little more than the market price alone.
What this snapshot is, and what comes next
These are prices for a buyer at one moment, not a recommendation. Prices keep moving until the outcome is known, so none of this describes the board now.
Delta Arc saved this exact snapshot. In a Monday follow-up on The Line, we will score these prices against the final results and see how the implied probabilities held up.
Sources: Delta Arc BM Dash; Kalshi fee schedule; Polymarket documentation; ESPN odds feed.
Sources
Outside pages cited in this post, in order of first citation
- Kalshi's fee schedulekalshi.com
- Polymarket's documentationdocs.polymarket.com
- ESPN's odds feedespn.com
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