Kalshi Vs Sportsbooks NFL: The Fee They Don't Quote

$40,480 hit the Steelers contract at 1:53 p.m. ET on Thursday, all of it inside one clock second, filled at 63¢ for a contract that was asking 72¢ by Saturday midday. Kalshi publishes every trade on its NFL game markets, so that order sits in the public record. The fee the buyer paid on top of 63¢ does not, because it is not in the price either: every one of these 28 team prices is quoted exactly one cent wide, and the fee sits outside that cent.

So I priced the fee. All 14 Week 1 games still to play, on Kalshi, on as many as 26 sportsbooks and on Polymarket US and ProphetX, pulled in the same minutes at 12:24 p.m. ET on Saturday, September 12, 2026, about a day before the early kickoffs, so the 1:00 games will have moved by the time you read this. The answer turns on one thing, whether you shop: line every book up and a sportsbook is cheaper than Kalshi on 23 of the 28 team prices once the fee is counted, but stay inside a single app and it is close to even, with the exchange cheaper on most favorites and the books cheaper on most underdogs.

The fee itself is Kalshi's published 7% × price × (1 − price) per contract, charged when you take a price someone else has already posted and rounded up to the next cent on the order: about 1.75¢ at a coin-flip price, about 0.63¢ on a heavy favorite, and never part of the quote. What it costs by market is in our Kalshi fee schedule, what it costs to fund and withdraw is in the Kalshi fees guide, and the plain-English guide to betting sports on Kalshi covers placing the order; every price below marked fee in is a venue's quote with its own fee added, which is the price where you get your money back. What that one second on Thursday cost the buyer in fees is at the bottom of this page.

The Board

Every side of the 14 games still to play, favorite first and then the underdog, at 12:24 p.m. ET on Saturday, September 12, 2026. Kalshi is from its order book; the sportsbooks, Polymarket US and ProphetX are from the OddsShopper odds screen in the same minutes. The last column is the cheapest place to buy that side once every venue's own fee is counted, exchanges included.

Kickoffs in Eastern time. Typical book is the median of the books quoting that side, 11 to 26 of them depending on the game; best book is the lowest price any of them posted. A real Kalshi order rounds its fee up to the next whole cent, so a small order pays slightly more than the tenths shown here.

One game carries the whole finding. The typical book wants 67.7¢ for a dollar of Bengals; Kalshi, fee in, wants 65.6¢ — the widest favorite gap on the board at 2.1¢. Flip to the other side of that same game and it reverses: the book sells the Buccaneers at 37.0¢ and the exchange, fee in, charges 38.6¢. Same shape of contract on both rows, $1 if the team wins. The difference is that the book pads one side and not the other.

These are market prices and model estimates, not predictions of fact and not financial advice.

Why Favorites And Underdogs Split

Kalshi's fee is symmetric. Seven percent of price times one minus price returns the same 1.47¢ at 30¢ as it does at 70¢, so the exchange charges the same to back a dog as a chalk. A book's margin is not symmetric, and it does not sit in the same place twice. Strip the vig out of the best two-sided line on each game and the typical book was 2.6¢ above fair on the Bengals and 2.1¢ above on the Buccaneers; on the game this page opened with it reversed, 1.6¢ on the Steelers and 2.4¢ on the Falcons. Kalshi wins wherever the book chose to load the side you want, which on this pull meant the exchange beat the typical book on 10 of 14 favorites while the typical book beat the exchange on 8 of 14 underdogs, one game tied. That is not a law about favorites. It is a record of where each book parked its margin on Saturday morning.

That is the answer for one app. Against FanDuel in particular, the book most of those bettors have, Kalshi with its fee counted won 14 of the 28 team prices, lost 13 and tied 1 — a coin flip, with most of the wins on favorites and most of the losses on underdogs. That head-to-head gets its own page, Kalshi against FanDuel on every NFL game, rebuilt from this same pull.

Shopping changes the result outright. Take the best price on each side, the fifth column above, and it beats Kalshi, fee in, on 23 of the 28 prices; Kalshi wins 5. That best price is often at a book not every reader can open, Circa most often on this slate. So here is the number for a reader whose phone holds the usual apps: strip the field back to DraftKings, FanDuel, BetMGM, Caesars, Fanatics, Hard Rock and ESPN Bet and the best of those still beats Kalshi, fee in, on 18 of the 28 prices they quote. Shopping the mainstream apps recovers most of the edge; shopping none of them is what makes the exchange look cheap. The live odds screen carries Kalshi as its own column beside the books, with the fee already inside its number, so the comparison above is one you can re-run on any game yourself.

Cheapest is not the same as worth betting, and on this slate it is worth saying plainly. Strip the margin out of the best two-sided line on the screen, the standard no-vig calculation, and Kalshi's fee-in favorite sits a median 1.7¢ above that fair price and its underdog 2.1¢ above; not one of the 28 prices is quoted under fair anywhere. On these 14 games you are choosing where to pay, not finding a bet. If you want the bet itself, OddsShopper's free expert picks are the conventional route, the daily prediction-markets-versus-sportsbooks board runs this comparison on baseball every morning, and the AI NFL predictions page puts a panel of models beside these same Kalshi prices.

The Other Two Exchanges

Kalshi is not the only exchange on the board. Polymarket US had a price on 7 of the 14 games at the time of the pull and ProphetX on 11; the rest had no two-sided quote there at the time of the pull. Before fees Kalshi's ask on the favorite is the lowest of the three on every shared game: ProphetX prices that side above Kalshi on 11 of the 11 games it quotes, Polymarket US on 7 of 7, and the three are never more than 2.5¢ apart.

The fees invert that. Polymarket US charges 6% × price × (1 − price) to whoever takes a posted price, a shade under Kalshi's 7%, while ProphetX takes 2% of net winnings and nothing on the way in, so its cost only lands if the trade wins; the ProphetX figures in the board are that fee converted to an entry-equivalent, the price at which the cut of the win leaves you even, which is the only way to line it up against a fee charged the moment you click. Count each venue's own fee and ProphetX is the cheapest exchange for the favorite on 9 of the 11 games with a second quote, Kalshi on 2, and the cheapest for the underdog on 11 of the 11. The exchange with the lowest quote is not the exchange with the lowest cost — which is the same trap, one venue over, as the one-cent spread.

New accounts: ProphetX 🎁 pays $75 in incentive funds after one $50 trade, and Polymarket US 🎁 pays a $50 bonus on a $10 deposit. Both are affiliate links and OddsShopper may earn a commission if you sign up through them. 18+ Only. Restrictions and eligibility requirements apply. Not available in all jurisdictions. Trading is risky. 100% loss can occur. See polymarket.com/tos for more information. The Polymarket US App serves as an independent software provider and affiliate of Polymarket US and Polymarket Clearing, the CFTC-regulated exchange and clearing organization.

Where The Money Went

Prices are a snapshot; the trade record is not. Across the 28 team markets on these 14 games, 6,046,753 contracts have changed hands, about $3.07 million spent taking a side, and 65 percent of those dollars bought a favorite at the posted price — paying the fee to do it. These are the six seconds that moved the most money.

The Falcons and Texans rows are the pair worth staring at: $15,021 and then $12,074, 44 seconds apart on Friday night, on two different games. Elsewhere the record shows the Falcons contract moving 11¢ from its first trade to its last, the largest move on the board, and the Commanders contract taking 96 percent of its $39,243 on one side. Kalshi publishes prices, not names, so I will not guess who any of them are.

Which leaves the order at the top of this page. $40,480 at 63¢ is about 64,254 contracts, and at Kalshi's published rate the fee on them came to roughly $1,048 — a sum that appears in no quote on the exchange and in none of the one-cent arithmetic that makes it look cheap. One order was 15 percent of every dollar that contract has ever taken, and the ask sits 9¢ above where it filled.

Know what a Kalshi price is worth before you take it.

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