# Fed Decision Odds, Scored: Polymarket vs Kalshi at Every 2026 FOMC Meeting
How Polymarket and Kalshi priced each 2026 FOMC decision, scored against the outcome. Both venues had the 16 September hike at 87.5% an hour out; the multi-outcome Brier was 0.029 on Polymarket and 0.031 on Kalshi. Next decision 27–28 October.
Canonical URL: https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi
Author: [Vultax Research](https://vultax.com/editorial-policy)
Published: 2026-09-06
Last public revision: 2026-09-16
Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Prices are the venues' quoted probabilities at the stated read time, not Vultax's view, and can change at any moment. Fill figures describe public on-chain activity observed by Vultax. Nothing here is a forecast or financial advice.
## Key figures
- Hike priced an hour before the decision: 87.5% — Both venues, 16 September 2026 17:00 UTC; the Fed raised 25 bp to 3.75–4.00% at 18:00 UTC. Multi-outcome Brier 0.029 Polymarket, 0.031 Kalshi, lower is better. The original 6 September study read the same Polymarket contract at 49.5%. The strip at the top of this page carries the latest available prices and the time they were read.
- Kalshi, 25 bp hike — 6 Sep: 49.0% — Original study, observed 2026-09-06 07:00 UTC. Hold 49.0%, cut 1.0%: last hourly candle close on KXFEDDECISION-26SEP.
- Largest daily gap, 30 days to 6 Sep: 3.5¢ — Polymarket minus Kalshi on the hike contract. The study's illustrative two-leg taker estimate at 50 cents was 2.75 cents; see the fees section for what that does and does not establish.
- Wallets on the three contracts, 7 days to 6 Sep: 5,120 — 13,659 fills, $5.90M notional; the round-the-clock cohort was 131 wallets making 19.8% of trades
## Scored: the 16 September decision
The FOMC raised the target range 25 basis points to 3.75–4.00% at 18:00 UTC on 16 September 2026. The two checkpoints below were locked by the forecast record before the announcement — 24 hours out and one hour out. The 14-day and 7-day checkpoints are absent because the record opened on 12 September.
Both venues had the hike as the clear favourite at both checkpoints, and what was left over sat almost entirely on “hold” rather than on a cut. Polymarket scored a little better at both, 0.029 against Kalshi’s 0.037 a day out and 0.031 an hour out, but the two sums run over different contract sets, so the gap is narrow rather than decisive.
The next decision is on 27–28 October 2026. The same two checkpoints will be read from the forecast record and scored here.
### Scored: the 16 September decision
Probability on the 25 bp hike contract at each checkpoint, taken from the forecast record before the announcement. Brier is the multi-outcome score summed over each venue’s contracts on the decision — four on Polymarket, two on Kalshi — so the sums are not strictly comparable; lower is better and a perfect call is 0.
| Checkpoint | Polymarket | Kalshi | Outcome | Brier, Polymarket / Kalshi |
| --- | --- | --- | --- | --- |
| 24 hours out — 15 Sep 18:00 UTC | 87.5% | 86.5% | Hike, 25 bp | 0.029 / 0.037 |
| 1 hour out — 16 Sep 17:00 UTC | 87.5% | 87.5% | Hike, 25 bp | 0.029 / 0.031 |
[CSV](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.csv?dataset=section-scored-16-september-2026-table) · [JSON](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.json?dataset=section-scored-16-september-2026-table)
## Original study — observed 6 September 2026, 07:00 UTC
The figures in this section are the observation the study was written on, kept as published. The strip at the top of this page carries the latest available prices for the same contracts, with the date and time each was read. Where the two differ, the strip is the newer reading.
At 2026-09-06 07:00 UTC on 6 September, Polymarket's September Fed decision event priced a 25 basis-point hike at 49.5% and no change at 49.5%, with a 25 bp cut at 0.4%. $99 million has traded on the event since it opened and $2.87 million of it in the last day. Kalshi's contracts on the same meeting closed their last hour at 49.0% for the hike, 49.0% for no change and 1.0% for a cut.
That is not two markets disagreeing. It is two markets saying the same thing with the precision of a coin, ten days before the Federal Open Market Committee meets on 15 and 16 September. The interesting number is not either probability but the distance between them, because that distance is what an arbitrage bot would be paid to close, and it has sat inside the fee floor for most of the month.
What changed since. The venues moved a long way from the coin flip this study recorded: by the day of the decision both had the 25 bp hike near 87.5%, and the section above scores those readings against the outcome. The strip at the top of this page now carries the remaining 2026 meetings, with the observation time on every figure.
### Probability of a 25 bp hike, Polymarket vs Kalshi
Last quoted price each day, 6 August to 6 September 2026. Polymarket from the CLOB price history; Kalshi from hourly candle closes.
| Category | Polymarket (%) | Kalshi (%) |
| --- | --- | --- |
| 08-07 | 36.5 | 35 |
| 08-08 | 35.5 | 35 |
| 08-09 | 35.5 | 33 |
| 08-10 | 43.5 | 45 |
| 08-11 | 39.5 | 40 |
| 08-12 | 32.5 | 34 |
| 08-13 | 27.5 | 31 |
| 08-14 | 24.5 | 26 |
| 08-15 | 24.5 | 26 |
| 08-16 | 24.5 | 27 |
| 08-17 | 27.5 | 31 |
| 08-18 | 28.5 | 29 |
| 08-19 | 27.5 | 27 |
| 08-20 | 27.5 | 29 |
| 08-21 | 30.5 | 32 |
| 08-22 | 30.5 | 31 |
| 08-23 | 31.5 | 32 |
| 08-24 | 34.5 | 34 |
| 08-25 | 32.5 | 33 |
| 08-26 | 32.5 | 32 |
| 08-27 | 30.5 | 30 |
| 08-28 | 50.5 | 50 |
| 08-29 | 44.5 | 47 |
| 08-30 | 52.5 | 53 |
| 08-31 | 54.5 | 56 |
| 09-01 | 57.5 | 60 |
| 09-02 | 53.5 | 54 |
| 09-03 | 42.5 | 45 |
| 09-04 | 49.5 | 52 |
| 09-05 | 49.5 | 50 |
| 09-06 | 49.5 | 49 |
[CSV](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.csv?dataset=section-original-study-observed-6-september-2026-07-00-utc-chart) · [JSON](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.json?dataset=section-original-study-observed-6-september-2026-07-00-utc-chart)
## Fees, liquidity and the price gap
The largest daily difference in the original comparison was 3.5 cents per dollar of payout. That exceeds the study's stated 2.75-cent fee estimate by 0.75 cents. It does not establish a profitable trade: these are historical price observations, and executable returns also depend on bid-ask spreads, available size, fees at each execution price, and equivalent settlement rules. This study did not measure an executable return after those costs.
How that estimate was built, and its limits. Polymarket charges takers C x feeRate x p x (1 - p) and charges makers nothing; Kalshi charges takers 0.07 x C x p x (1 - p). Under the illustrative coefficients this study used, at 50 cents that is 1.00 cent per contract on the first venue and 1.75 on the second, so 2.75 cents for a two-leg taker round trip before slippage. A 0.05 coefficient on the first venue would instead give 1.25 + 1.75 = 3.00 cents. [Polymarket's current documentation](https://docs.polymarket.com/trading/fees) lists 0.04 for Finance and Politics and 0.05 for Economics, so a single blanket rate for this contract is not safe to assert; the exact fee parameters that applied to this contract on the observation date are not verified here. Two entries held to settlement are also not the same cost calculation as opening and later closing both positions. Treat these as conditional examples, not as a verified cost for this market.
In July, Vultax watched the same two venues on matched Fed-rate contracts every 85 seconds for a day and found that [the one exactly matched pair held a 5.7-cent gap that never closed](https://vultax.com/research/kalshi-polymarket-open-interest-by-category); the September decision contracts are better matched, resolve on the same announcement, and are correspondingly tighter. Where there has been a lean it has been Kalshi's: on most days this month its hike contract traded a cent or two above Polymarket's, consistent with a US-regulated venue whose traders weight the public case for a hike that Fed governors have been making, against a global venue that priced the hold more heavily until this week.
### Polymarket minus Kalshi on the hike contract, cents
Daily, last price. The fee floor for a two-leg taker round trip at 50 cents is about 2.75 cents either way.
| Category | Gap, cents |
| --- | --- |
| 08-07 | 1.5 |
| 08-08 | 0.5 |
| 08-09 | 2.5 |
| 08-10 | -1.5 |
| 08-11 | -0.5 |
| 08-12 | -1.5 |
| 08-13 | -3.5 |
| 08-14 | -1.5 |
| 08-15 | -1.5 |
| 08-16 | -2.5 |
| 08-17 | -3.5 |
| 08-18 | -0.5 |
| 08-19 | 0.5 |
| 08-20 | -1.5 |
| 08-21 | -1.5 |
| 08-22 | -0.5 |
| 08-23 | -0.5 |
| 08-24 | 0.5 |
| 08-25 | -0.5 |
| 08-26 | 0.5 |
| 08-27 | 0.5 |
| 08-28 | 0.5 |
| 08-29 | -2.5 |
| 08-30 | -0.5 |
| 08-31 | -1.5 |
| 09-01 | -2.5 |
| 09-02 | -0.5 |
| 09-03 | -2.5 |
| 09-04 | -2.5 |
| 09-05 | -0.5 |
| 09-06 | 0.5 |
[CSV](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.csv?dataset=section-fees-liquidity-and-the-price-gap-chart) · [JSON](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.json?dataset=section-fees-liquidity-and-the-price-gap-chart)
## Who is trading it
Over the last seven days Vultax's pipeline observed 13,659 fills worth $5.90 million on the three September contracts, from 5,120 wallets. 131 of those wallets belong to the round-the-clock cohort from [the cadence study](https://vultax.com/research/polymarket-wallets-that-never-sleep-trading-cadence), 2.6% of the wallets on the contract, and they made 19.8% of the trades and 8.3% of the notional. Across all of Polymarket that cohort makes 58% of trades; on the Fed markets it makes a fifth. By Polymarket's standards the Fed is unusually human.
The fills arrive in bursts around the data. Friday's jobs report is the tallest hour of the week; the August CPI print landed on 11 September at 08:30 ET (12:30 UTC), the last scheduled macro release before the meeting.
### Who is trading it
Read 2026-09-06 07:00 UTC, 6 September 2026. Kalshi tickers KXFEDDECISION-26SEP-H25, -H0, -C25.
| Contract | Polymarket | Kalshi | Polymarket volume |
| --- | --- | --- | --- |
| 25 bp hike | 49.5% | 49.0% | $18.5M |
| No change | 49.5% | 49.0% | $23.2M |
| 25 bp cut | 0.4% | 1.0% | $30.7M |
[CSV](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.csv?dataset=section-who-is-trading-it-table) · [JSON](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi/data.json?dataset=section-who-is-trading-it-table)
## What to watch into the October meeting
Four things decide the next one, on 27–28 October 2026.
- The last scheduled macro print before the meeting - on the equivalent release before the July decision the hike contract moved eight cents, and before September's it moved less than two.
- The gap, not the level - if Polymarket and Kalshi separate by more than three cents on the same contract, one of them is being moved by a large order, and the level alone tells you nothing.
- The cut contract - at under a cent it is the cheapest lottery ticket on either venue; a move above two cents means someone believes something the venues do not.
- Post, do not take - on a coin flip the taker fee is the whole edge; a resting order on Polymarket pays no fee at all.
## How to read the live figures
The strip at the top of this page is republished every ten minutes from Polymarket's event and price history, Kalshi's contracts and candlesticks, Manifold and PredictIt on the same question, the Treasury bill curve against the funds rate, the Cleveland Fed's daily inflation nowcast, the Fed's own press and speech feeds, and Vultax's record of Polymarket fills. Each figure carries the time it was observed, which is not the same as the time the pack was published. The Vi IQ beneath it scores the six domains the Vultax terminal scores for a pair, computed for this page's subject from published inputs, with a domain that cannot be computed shown as unavailable rather than filled in. Some inputs go stale on their own schedule: when Vultax's observed-fill record is behind, the strip says so rather than presenting the provider prices and the fill-derived figures as equally fresh.
The four figures are the two venues' prices for a 25 bp hike, the probability-weighted expected move in basis points across all five outcomes, and the dollars traded on the event in the last day. Behind them the pack carries the October and December meetings on both venues, the four-venue spread once Manifold and PredictIt are included, and the bill market's own implied move, which has run more hawkish than either prediction venue for most of the month.
## Context from elsewhere
The July minutes explain why the September contract is close. The Committee held at 3½–3¾% by nine votes to three, with Hammack, Kashkari and Logan preferring a quarter-point hike, described inflation as elevated in part because of energy supply shocks, and recorded staff risks to inflation skewed to the upside. By early August J.P. Morgan's wealth-management desk had futures pricing roughly a 65% chance of a September hike, with oil near $80 and the Strait of Hormuz still disrupted; the prediction venues have since drifted back toward even money as the data softened.
There is also a record of how good these particular contracts are. A 2026 study of Kalshi's macro markets found federal-funds-rate contracts near-perfectly calibrated by decision day, with a Brier score of 0.0001 against 0.0987 across all macro series, and found the same markets far less informative a month out than an hour out (0.1587 against 0.0812). A coin flip nine days before the meeting is therefore not a failure of the market; it is the market saying the decision is genuinely open, and the price on the morning of the 16th is the one that has historically been right.
The venues themselves are changing under the contract. Polymarket launched perpetual futures on 3 September and Kalshi has said it plans rates and FX futures, so a Fed decision may soon trade on the same platforms as the instruments that hedge it; the U.S. app that Polymarket opened in December 2025 and took off its waitlist in May 2026 remains sports-first.
## Method and limits
Polymarket prices are the CLOB price history for each contract's Yes token at hourly fidelity; Kalshi prices are hourly candle closes from its public trade API. Both were read at the time stamped above for the figures in the body; the strip at the top of this page and the interactive edition re-read the same sources every ten minutes, and the interactive edition carries the full hourly series. Fill counts come from Vultax's copy of public on-chain fills and undercount fills not yet ingested at read time. Fee rates are as published by each venue on 5 September 2026. Nothing here is a forecast of the decision, and nothing here is financial advice.
## Questions
### What are the odds of a Fed rate hike in September 2026?
The strip on this page shows Polymarket's and Kalshi's latest available prices for a 25 bp hike, each with the time it was observed, alongside the full five-outcome distribution and the probability-weighted expected move. Manifold and PredictIt prices for the same question are in the pack behind the page.
### Why do Polymarket and Kalshi price the Fed differently?
Different traders, different fee structures and different access rules: Kalshi is a U.S.-regulated exchange, Polymarket's main venue is offshore. Gaps of a cent or two are normal and rarely worth the round trip; the article measures the gap and the fee floor.
### How accurate are prediction markets on Fed decisions?
Market prices express uncertainty and can change as the decision approaches. This page follows one event; it cannot establish either platform's overall forecasting accuracy. Published research should be read with its sample and forecast horizon in mind: the 2026 Kalshi macro study cited below reports a Brier score of 0.0001 on federal-funds-rate contracts against 0.0987 across all macro series, and finds prices a month out much less informative than an hour out.
### What could move the odds before 16 September?
The August CPI release on 11 September, energy prices tied to the Strait of Hormuz, and any Fed communication before the blackout. The pack behind this page carries the Fed's press and speech feeds and the Cleveland Fed nowcast for that reason.
## Revision notes
- 2026-09-07: Live figures and a Vi IQ for this subject now refresh every ten minutes on this page from outside sources and Vultax's own tables; a context section, the questions below and these revision notes were added.
- 2026-09-07: Added the July FOMC minutes, the early-August futures pricing and the 2026 Kalshi macro-calibration study as context; the pack now carries October and December on both venues, Manifold and PredictIt, and the bill-implied move.
- 2026-09-12: Retitled for the question the page answers and shortened the opening. The 6 September observation is now labelled as the original study and the live strip carries the latest available prices with full observation times, a five-outcome comparison and explicit stale and unavailable states. The August CPI date is stated as 11 September (BLS), and the fees section now reads the 3.5-cent gap against the study's 2.75-cent illustrative estimate without treating the difference as an executable profit.
- 2026-09-16: Scores the 16 September decision against the 24-hour and 1-hour checkpoints on both venues, and opens the page onto the remaining 2026 meetings.
## Sources and methodology
- [Polymarket: Fed decision in September?](https://polymarket.com/event/fed-decision-in-september-762) — Event and contract prices, Gamma and CLOB APIs; read 2026-09-06
- [Kalshi: KXFEDDECISION-26SEP](https://kalshi.com/markets/kxfeddecision) — Hourly candles via the public trade API; read 2026-09-06
- [Polymarket trading fees](https://docs.polymarket.com/trading/fees.md) — Formula and per-category rates
- [Kalshi fee schedule](https://kalshi.com/fee-schedule) — Taker formula
- [Vultax: Kalshi vs Polymarket odds gap, measured](https://vultax.com/research/kalshi-polymarket-open-interest-by-category) — The July matched-pair study
- [Vultax: 1.6% of Polymarket wallets never sleep](https://vultax.com/research/polymarket-wallets-that-never-sleep-trading-cadence) — The round-the-clock cohort
- [Federal Reserve — Minutes of the FOMC, July 28–29, 2026](https://www.federalreserve.gov/monetarypolicy/fomcminutes20260729.htm) — 9–3 to hold at 3½–3¾%; Hammack, Kashkari and Logan preferred a quarter-point hike; inflation 'elevated' with energy supply shocks; staff saw inflation risks skewed to the upside.
- [J.P. Morgan Wealth Management (Chase) — September 2026 rate hike now expected amid energy shocks (5 Aug 2026)](https://www.chase.com/personal/investments/learning-and-insights/article/september-2026-rate-hike-now-expected-amid-energy-shocks) — Futures priced roughly a 65% chance of a September hike in early August; oil near $80 with the Strait of Hormuz still disrupted.
- [Krause — Calibration and Forecast Accuracy of Macroeconomic Prediction Markets: Evidence from Kalshi, 2025–2026 (SSRN)](https://papers.ssrn.com/sol3/papers.cfm?abstract_id=7117919) — 594 Kalshi macro markets, 1,860 observations, nine series: overall Brier 0.0987; federal-funds-rate markets near-perfectly calibrated (0.0001); unemployment-rate markets the weakest (0.1302); one-hour horizon 0.0812 against 0.1587 at thirty days, as summarised in the abstract.
- [Coinpaprika — Polymarket expands beyond prediction markets with 20x leverage perps (Sep 2026)](https://coinpaprika.com/news/polymarket-expands-beyond-prediction-markets/) — Perpetual futures launched 3 September 2026 with up to 20x leverage; 67 markets within hours; U.S. traders barred. Kalshi's bitcoin perpetuals went live 3 June 2026.
- [Finance Magnates — Polymarket rolls out U.S. app after CFTC green light, starting with sports](https://www.financemagnates.com/forex/polymarket-rolls-out-us-mobile-app-after-cftc-green-light-starting-with-sports-events/) — Polymarket US launched 2 December 2025 on the QCEX designation acquired for $112 million; the invite waitlist was removed in May 2026; iOS only at the time of writing.
Changing market context is available on the [article page](https://vultax.com/research/fed-september-decision-coin-flip-polymarket-kalshi). It is separate from the published study exported here.