A 51-cent Kalshi contract at −104 costs −112 once the taker fee is added.
01 · How contracts work
A contract is a price and a probability at once
On Kalshi, Polymarket and similar venues you buy a yes or no contract that pays $1 if it settles your way. The price in cents is the market's probability: a 51-cent contract says 51%. Converting to American odds is the same arithmetic as for any price: 51 cents is about −104.
Unlike a sportsbook, the venue does not build its margin into the price. It charges a fee per trade on top. That makes the shown price look cheaper than the sportsbook's, and it is why the screen price is the wrong number to compare.
02 · What the fee does
What the fee does to the price
Worked example · 100 contracts at 51 cents, football game market
- Contracts
- $51.00
- Kalshi taker fee
- $1.75
- Total paid
- $52.75
- Payout if it wins
- $100.00
- Break-even chance after the fee
- 52.75%
- All-in price
- −112
Kalshi's taker fee is 7% of price × (1 − price) per contract for takers, a quarter of that for resting orders, rounded up to the cent. It is largest near 50 cents and shrinks toward the ends, so even-money contracts pay the most fee. A resting (maker) order pays a quarter of it: the same 100 contracts cost −106 all in.
| Venue and role | Fee | All-in price |
|---|---|---|
| Kalshi, taker | $1.75 | −112 |
| Kalshi, resting order | $0.44 | −106 |
| Polymarket US, taker | $1.74 | −112 |
03 · Real betting legs
Exchanges are real legs, once the fee is counted
Because the fee is visible and separate, an exchange price after fees is a genuine alternative to a sportsbook price. It can be the best price on the board, and it can be one leg of an arbitrage or a middle. Our desks count exchange prices as bettable legs only after the fee, so a price that looks best on the screen but loses after the fee is never shown as best.
- Liquidity is thin on props. The price you see may only be good for a few contracts. Bigger orders walk up the book.
- Settlement rules differ. Read how a market settles a push, a void or an overtime result before treating it as the same bet as a sportsbook line.
- Fees depend on role. Resting orders pay less (or nothing on some venues) but may not fill.
Before you bet
What this means for your next bet
- Turn the contract price into American odds, then add the fee for your size and role.
- Compare the all-in price with the best sportsbook price, never the screen price.
- Check how much size is available at the price before you count on it.
- Read the settlement rules for pushes, voids and overtime.
Questions3 questions
How much are Kalshi fees on sports contracts?
Kalshi charges takers 7% of price × (1 − price) per contract for takers, a quarter of that for resting orders, rounded up to the cent. On 100 contracts at 51 cents in a football game market that is $1.75, which turns a shown −104 into −112 all in.
Are prediction market odds better than sportsbook odds?
Sometimes. The shown price usually looks better because the fee is charged separately. Compare the price after the fee: when it still beats the best sportsbook price, the exchange is the better bet.
Can you use Kalshi or Polymarket for arbitrage?
Yes, if the prices still form an arbitrage after the exchange fee and there is enough size at the price. Many apparent exchange arbs disappear once the fee is counted.
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Dynatyze is analytics and education for people 21 and over. It is not a sportsbook and never takes a bet. Every number on this page describes the past or the arithmetic of a price; none of it promises a result, and results vary.
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Research and education only. Results vary, and nothing here promises a profit. Every number from our own data names its sample and its dates; every worked example is the arithmetic of the prices shown.