Prediction markets just had a $22.2 billion week. Here is what the number actually counts.
The records, and which days they belong to
Three numbers landed within about 24 hours, and they describe different periods.
The $8.56 billion two-day record is Bloomberg's count of Kalshi plus Polymarket over what it calls last weekend's NFL and college slates. Aldrin Research's count for 3-4 October, published by Covers, had all eleven tracked venues at $9.43 billion, with Kalshi at $3.45 billion on Saturday and a then-record $3.68 billion on Sunday. Kalshi plus roughly $1 billion across Polymarket's two venues fits the Bloomberg figure, so we read it as the 3-4 October weekend rather than the one just finished.
The $22.2 billion weekly record is for the two companies combined. For 28 September to 4 October, DeFi Rate separately counted $18.37 billion on Kalshi, $2.71 billion on Polymarket US and $519 million on Polymarket's international venue, about $21.6 billion on three different calendars. Bloomberg's week is either that one on a different convention or the week ending 11 October. Either way, the direction is the same.
The $3.9 billion Saturday is a Kalshi-only figure for 10 October from TickerTracker, posted by Dustin Gouker and relayed by Prediction News. If it holds, it beats the record set six days earlier and is the sixth $3 billion day since the NFL season began on 10 September.
How we got here in six weeks
DeFi Rate's weekly series, which values Kalshi contracts at $1 face and uses UTC weeks, shows the exchange doubling since late August, with the inflection exactly where the NFL calendar says it should be.
| Week ending | Kalshi | Polymarket US | Polymarket (intl) | Football context |
|---|---|---|---|---|
| 23 Aug | $9.06bn | $876m | $597m | Preseason |
| 30 Aug | $10.17bn | $895m | $551m | College Week 1 |
| 6 Sep | $11.86bn | $975m | $487m | NFL Week 1 begins 10 Sep |
| 13 Sep | $12.98bn | $1.66bn | $540m | NFL Week 1 weekend, $4.9bn |
| 20 Sep | $15.27bn | $2.34bn | $548m | NFL Week 2 weekend, about $6bn |
| 27 Sep | $15.66bn | $2.83bn | $488m | NFL Week 3 |
| 4 Oct | $18.37bn | $2.71bn | $519m | NFL Week 4, $9.43bn weekend |
Kalshi's weekly notional rose 102.65 percent over six weeks. Polymarket US tripled and then slipped 4.41 percent in the latest week, the first decline in the series, while Polymarket's international venue has been flat at about half a billion dollars. Almost all of the industry's growth is one venue, and almost all of that venue's growth is one product category.
What is actually in the $18.37 billion
DeFi Rate's category breakdown for 28 September to 4 October is the clearest public view of where the volume sits.
| Category | Volume | Share | Week on week |
|---|---|---|---|
| Exotics (combos and multi-leg) | $11.82bn | 64.3% | +24.9% |
| Sports (single markets) | $3.64bn | 19.8% | +1.3% |
| Crypto | $2.42bn | 13.2% | +7.4% |
| Commodities | $275m | 1.5% | +24.4% |
| Financials | $83m | 0.5% | +646% |
| Economics, politics, mentions, science | under $40m | 0.2% | mixed |
Exotics grew by $2.35 billion in a week, about 87 percent of Kalshi's total increase. The largest single market was a 10-leg NFL combo at $117.16 million; the biggest single-game market, Philadelphia to beat Chicago, traded $50.67 million. Economics, the category Kalshi was founded on, was $19.34 million, about one thousandth of the week.
Bloomberg's figures agree: combos were 65 percent of Kalshi's trading and 53 percent of Polymarket's US activity in the past week, and Kalshi's Elisabeth Diana said at least 96 percent of its combos relate to sports. Piper Sandler put Kalshi's combo volume on heavy football days at about $1.36 billion, more than double a non-football day. For scale, total combo volume across the whole previous NFL regular season was roughly $900 million. Kalshi now does more than that on a single Saturday.
Notional versus money: the 5.7-to-one gap
Every figure above is notional. A Kalshi contract pays $1 if its event happens, and notional counts each contract at that $1 regardless of what the buyer paid. For a market priced at 50 cents, notional is twice the money changing hands. For a 10-leg parlay priced at two cents, it is fifty times. Aldrin Research publishes both measures, and Sunday 4 October is the only day we have seen side by side.
| Sunday 4 October, Kalshi | Figure |
|---|---|
| Notional volume (contracts at $1) | $3.68bn |
| Dollar volume (contracts at price paid) | $643.1m |
| Money paid per $1 of notional | about 17.5c |
| Combo contracts, notional | $3.1bn |
| NFL single-game markets, notional | $861.4m |
| Kalshi share of all venues' Sunday notional | 73.7% |
Two things follow. First, the "$22.2 billion week" probably represents something in the region of $4 billion actually staked, if the Sunday ratio is representative, and less on days when combos are a larger share. That is still a very large number for a venue that did not list sports contracts until January 2025, but it is a different number. Second, the gap is probably widening: Kalshi's dollar volume on 4 October rose nearly 10 percent on the week while all-venue Sunday notional rose 12.1 percent, and the exotics share keeps climbing.
Neither measure is wrong. Notional is how derivatives exchanges have always reported. But it is not comparable to a sportsbook's handle, which counts money wagered, and most of the week's coverage compared the two.
Why the measurement is now a regulatory question
The volume figure sits in the middle of three live fights, and each side reads it differently.
The CFTC. On 9 October the agency published a rule excluding licensed sportsbook and casino bets from the swap definition and a proposal writing event contracts in. Both cite volume figures, and as we noted at the time, the ones they cite do not match the industry's. A parlay-heavy venue is also exactly the product the agency has worried aloud about; Prediction News reported that most parlay buyers finished the record 19-20 September weekend with losses.
The states and the NFL. At least 44 states say these contracts are sports wagering, and the NFL's 8 October Supreme Court brief asks for a 21-plus age floor and state oversight. For them, $22.2 billion is evidence that a sportsbook-scale market runs without state licences or New York's 51 percent tax. The notional-versus-dollar gap cuts the other way: the untaxed base is smaller than the headline.
Kalshi. The exchange argues it is not gambling because it matches buyers and sellers rather than taking the other side. Combos complicate that. Bloomberg and Prediction News both point to FanDuel acting as a market maker for Kalshi during the record weekends, and a market maker on a two-cent ten-leg parlay is, economically, taking the other side of a long-shot bet. Kalshi is also exploring an IPO after a round at about $40 billion, and its decision to shut its volume incentive programme a year early suggests it knows which numbers investors will look at hardest.
What to watch for
DeFi Rate's next weekly report, due around 13 October, will show whether the week ending 11 October is the $22.2 billion week and whether exotics crossed two thirds of Kalshi's volume.
Aldrin's Sunday 11 October count will give a second notional-to-dollar ratio to compare with 17.5 cents.
The CFTC's 30-day comment windows on the 9 October rules close in early November. Expect both sides to file volume figures, and expect them to be different numbers.
Method and limits
Headline records are from Bloomberg's 11 October report, read through Briefs Finance's same-day summary and two newswire relays rather than the original; the relays do not state the boundaries of the record week. Our assignment of the $8.56 billion weekend to 3-4 October is an inference from Aldrin Research's venue counts. Weekly and category figures are DeFi Rate's, which use UTC weeks and $1 face value for Kalshi, official business dates for Polymarket US and execution-price dollar volume for Polymarket, so the columns in our first table are not strictly additive. The 17.5-cent ratio is Aldrin's dollar volume divided by notional for one day, 4 October; applying it to a week is an illustration, not a measurement. The $3.9 billion Saturday figure is a TickerTracker tally relayed secondhand and not confirmed by Kalshi. Combo shares from Bloomberg, DeFi Rate and TickerTracker cover different periods and definitions. Nothing here is legal, financial or betting advice.
Frequently asked questions
How much did prediction markets trade last week?
Bloomberg put the combined weekly volume of Kalshi and Polymarket at a record $22.2 billion, with back-to-back daily records totalling $8.56 billion over one football weekend. For 28 September to 4 October, DeFi Rate counted $18.37 billion on Kalshi, $2.71 billion on Polymarket US and $519 million on Polymarket's international venue.
Is $22.2 billion the amount of money people bet?
No. It is notional volume, which values every contract at $1. On Sunday 4 October, Aldrin Research counted $3.68 billion of notional on Kalshi but $643.1 million of dollar volume, about 17.5 cents paid per notional dollar. Parlay-style combos priced in cents are the main reason for the gap.
What share of prediction market volume is parlays?
Bloomberg reported combos at 65 percent of Kalshi's trading and 53 percent of Polymarket US in the past week. DeFi Rate put exotics at 64.34 percent of Kalshi volume for 28 September to 4 October, and TickerTracker put parlays above 70 percent of Kalshi's $3.9 billion on Saturday 10 October.
Why does the volume measurement matter for regulation?
Both sides of the legal fight cite volume. Kalshi uses it to show deep, federally supervised markets; the states and the NFL use it to show sportsbook-style wagering on an untaxed venue. If notional overstates money at risk by about five to one, the market is smaller than the headlines, but more concentrated in the parlay products the CFTC's new rules single out.
How fast is Kalshi's volume growing?
From $9.06 billion in the week ending 23 August to $18.37 billion in the week ending 4 October, up 102.65 percent in six weeks, nearly all of it since the NFL season began. Polymarket US went from $876 million to $2.71 billion over the same span.
Sources
- Briefs Finance, Football bets are turbocharging prediction markets. Now the refs are lawyers., 11 October 2026, summarising Bloomberg, Kalshi, Polymarket's NFL surge draws scrutiny over sports betting rules, 11 October 2026.
- DeFi Rate, Kalshi volume reaches $18.37B, up 17.28% for Sept. 28-Oct. 4, 6 October 2026.
- Covers, Kalshi records new volume highs, all trading surpasses $9B weekend of NFL Week 4, 5 October 2026, citing Aldrin Research.
- Prediction News, Kalshi records $3.9 billion single-day volume as parlays drive NFL surge, 11 October 2026, and Kalshi hits $6B NFL weekend record on longshot parlay flow, 21 September 2026.
- ChainCatcher, Kalshi and Polymarket trading volume reached $8.56 billion in two days, 12 October 2026 (Bloomberg relay).
- BetG8, The CFTC wrote casino bets out of the swap definition, The NFL told the Supreme Court sports contracts are not swaps and Kalshi is ending its volume rewards a year early.
18+ only. This page reports published volume data and public statements. It is not legal, financial or betting advice. If gambling stops being fun, help is available at 1-800-GAMBLER.