Low fees don't make a losing strategy profitable — they just make it lose more slowly. You can lose everything you deposit. Trade only money you can afford to lose.
Why fees matter more in sports than anywhere else
Sports markets settle fast and often. An NFL fan might place 50 trades in a season; an MLB postseason trader might place 30 in five weeks. Small per-trade costs compound. A 1% leak per trade over 50 trades eats a meaningful chunk of a small bankroll even if your picks are roughly break-even.
How the Polymarket US sports fee works
At the time of writing, Polymarket US charges takers (orders that fill immediately against a resting order) a fee on sports contracts of roughly:
fee per contract ≈ 0.05 × price × (1 − price)
Makers (orders that rest on the book and get filled later) receive a rebate of roughly a quarter of the taker fee instead of paying it. The international Polymarket site uses a different sports fee schedule, and both have changed during 2026 — the formula shape (highest at 50¢, lowest at extremes) is what to remember.
Fee per contract at common prices
- 10¢ or 90¢: 0.05 × 0.10 × 0.90 = 0.45¢
- 25¢ or 75¢: 0.05 × 0.25 × 0.75 = 0.94¢
- 40¢ or 60¢: 0.05 × 0.40 × 0.60 = 1.20¢
- 50¢: 0.05 × 0.50 × 0.50 = 1.25¢ (the maximum)
Break-even win rates
If you buy "Yes" at price p and pay fee f, you need a true win probability above p + f to profit over time (ignoring the spread you cross, covered below).
- Buy at 30¢: fee 1.05¢ → break-even 31.1%
- Buy at 50¢: fee 1.25¢ → break-even 51.3%
- Buy at 60¢: fee 1.20¢ → break-even 61.2%
- Buy at 75¢: fee 0.94¢ → break-even 75.9%
- Buy at 90¢: fee 0.45¢ → break-even 90.5%
Notice the relative cost: at 50¢, the fee is 2.5% of your stake. At 90¢ it's only 0.5% of stake — but you're risking 90¢ to win 10¢, so a single upset wipes out nine wins.
Polymarket vs. a sportsbook -110 line
A standard sportsbook spread line of -110 on both sides means you risk $110 to win $100. Your break-even win rate is 52.4%. On a true 50/50 game, the book's hold is about 4.5%.
A 50¢ Polymarket contract with a taker fee has a break-even of about 51.3%. As a resting maker who earns a rebate, it's closer to 49.7%–50.5% depending on how much of the spread you give up. For coin-flip games, Polymarket is roughly half the cost of standard sportsbook juice — and less if you trade as a maker.
Placing a limit order a cent below the current ask means you (a) avoid the taker fee, (b) may earn a rebate, and (c) buy a cent cheaper. On a 55¢ MLB favorite, that's roughly 2.2¢ of total improvement — enough to flip a marginal trade from negative to positive expected value. The trade-off: your order might not fill, and it can get picked off if news breaks. Cancel resting orders before lineup cards, inactives, or starting-pitcher news.
The hidden cost: the spread
Every market has a bid (highest buyer) and ask (lowest seller). If the Chiefs trade at 67¢ bid / 68¢ ask and you buy at 68¢ then immediately want out, you sell at 67¢ — a 1¢ round-trip loss before fees. Big NFL and World Series markets usually have 1¢ spreads; props and low-volume markets can have 3–8¢ spreads, which quietly costs far more than the fee.
Round-trip math: in and out before settlement
One of Polymarket's advantages is you can sell before a game ends. But selling as a taker costs a second fee. Buy at 45¢ (fee ~1.24¢), sell at 55¢ (fee ~1.24¢) → you captured 10¢ of movement but paid ~2.5¢ in fees plus whatever spread you crossed. Frequent in-and-out trading on small moves is a fee grinder.
A quick pre-trade checklist
- What's my honest probability? (Written down before looking at the price.)
- Price + fee + half the spread — is my number clearly higher (for a buy)?
- Is the gap at least 3–5¢? Smaller gaps are usually noise in your estimate.
- Can I place a limit order instead of taking?
- Is the size 1–3% of my bankroll or less?
Bottom line
Polymarket's sports fees are genuinely low — roughly half a -110 sportsbook line at the 50¢ midpoint, and lower still if you rest limit orders. But fees are only part of the cost; the spread, round-trip trading, and overconfidence in your own numbers usually cost more. Run the math before each trade, trade as a maker, and apply it to the MLB postseason and NFL season playbooks. For taxes on any gains, use the side hustle tax calculator.