Polymarket arbitrage means buying a set of positions that pays more than it costs whatever happens, for example all the outcomes of an event for less than $1 in total, or the same question on Polymarket and Kalshi at prices that leave a gap after fees. True arbitrage is rare, small and closed within seconds by bots; most apparent gaps disappear once you add taker fees, spreads, the time your money is locked up and differences in the rules. Nimb does not run arbitrage or recommend it; this page explains the arithmetic.
What kinds of Polymarket arbitrage are there?
| Type | Example | Why it usually fails |
|---|---|---|
| Yes + No below $1 | Yes ask 0.48, No ask 0.50: pay 0.98, receive 1.00 | The order book matches them first; almost never available |
| All outcomes below $1 | In a neg-risk event, buy Yes on every outcome for 0.97 in total | Taker fee on each leg; thin outcomes; an "other" outcome may be missing |
| Deadline ladders | "By March" priced above "by June" for the same event | Rare and closed fast; Nimb checks ladders on every build |
| Across venues | Polymarket 41%, Kalshi 45% on "the same" question | Different rules, fees, custody; money must sit on both venues; eligibility |
| Related markets | Primary winner vs nominee vs general election | Not a true arbitrage: depends on modelling, not on a guarantee |
How do fees change the arithmetic?
Take a three-outcome politics event with Yes asks of 0.30, 0.33 and 0.34, total 0.97. Polymarket's taker fee per share is 0.04 × p × (1 − p): 0.0084, 0.0088 and 0.0090, total 0.0262. The set now costs 0.9962 for a $1 payout: 0.38% before any builder fee, spread movement or the months the money waits for resolution. At 4% a year on cash, three months of waiting is worth about 1%: the "arbitrage" loses to doing nothing. Geopolitics markets have no taker fee, which is why the rare true gaps tend to appear and vanish there. Fees.
What about Kalshi–Polymarket arbitrage?
- Rules. The two questions must resolve on the same event, source, deadline and time zone. Small wording differences have produced opposite results.
- Fees. Kalshi charges 0.07 × C × P × (1 − P) on takers; Polymarket by category. Both legs pay.
- Capital. You need dollars on Kalshi and pUSD on Polymarket, both locked until resolution.
- Eligibility. Few people can legally use both; Polymarket's international platform is close-only in the US. Polymarket vs Kalshi.
A persistent gap between venues is often information: it tells you the price is uncertain, or the rules differ.
Where does Nimb help?
Nimb checks date ladders (an earlier deadline should never be priced above a later one) and shows related markets with dashed theme lines and tested links (markets that move together). These are readings, not trade signals.
Frequently asked questions
Is Polymarket arbitrage risk-free?
Almost never. Fees, fills at worse prices, rule differences, resolution disputes and locked capital are all risks.
Do arbitrage bots make money on Polymarket?
Some professional traders do, with low latency, large capital and maker rebates. The opportunities left for retail traders are small.
Is arbitrage allowed on Polymarket?
Trading related positions is allowed; manipulation and wash trading are not.
Last reviewed 8 November 2026 · Data from Polymarket · Not financial advice · Nimb is not affiliated with Polymarket.