Polymarket and Kalshi price the Fed's October decision 4 points apart

October prices diverge across venues

Polymarket and Kalshi put the likelihood of an unchanged Fed rate in October four percentage points apart in a snapshot taken at 07:46 UTC on 15 October 2026, according to an analysis published on dev.to. The comparison used public API data collected through the prediction_markets tool in canli-mcp, with “probabilities” calculated as bid-ask midpoints rather than independent forecasts.

Polymarket’s unchanged-rate contract showed a 0.75 bid and 0.76 ask, implying 75.5%, versus Kalshi’s 0.71 bid and 0.72 ask, implying 71.5%. For a 25-basis-point increase, Polymarket quoted 0.24/0.25, compared with Kalshi’s 0.26/0.29.

The October event on Polymarket had recorded about $40.5 million in trading, while Kalshi’s had traded about 11.1 million contracts, each paying $1 if its outcome occurs. The four-point difference exceeded the quoted spreads of one to three cents. According to dev.to, differences in fees, trader eligibility and precise resolution terms could help explain why the venues’ prices remained apart.

A second discrepancy within Kalshi

Kalshi’s separate market for the Fed funds rate after the October meeting also differed from its main decision market. A contract for a rate above 4.00% quoted 0.22/0.25, giving a 23.5% midpoint. With the current target range at 3.75% to 4.00%, the analysis treated a move above 4.00% as requiring an increase. Yet hike outcomes in the main market totaled 28%: 27.5% for a 25-basis-point rise and 0.5% for a larger increase.

The threshold contract’s 0.25 best ask was below the 0.26 best bid for the 25-basis-point hike contract. But the threshold market had traded only about 0.37 million contracts, against 11.1 million in the main October event. The dev.to author had not checked the contracts’ exact settlement terms, leaving open whether their rules explain the discrepancy.

Trading activity was also lower in Polymarket’s later-dated markets: about $3.5 million for December and about $0.5 million for January. The analysis cautioned that a single trade could move prices in these smaller markets, making trading volume an important companion to any headline percentage.

What it means for prediction markets

• Venue attribution matters: The same October hold question produced midpoint prices of 75.5% on Polymarket and 71.5% on Kalshi at the recorded snapshot.
• A price gap is not automatically an equivalent-contract opportunity: Fees, access restrictions and settlement terms need to be distinguished from differences in trader expectations.
• Market structure affects interpretation: Kalshi’s thinner threshold market differed from its main decision market, while Polymarket’s December and January markets had substantially less trading than October.
• These are timestamped prices: The figures reflect bid-ask midpoints before fees and spread costs, not forecasts or necessarily executable prices.