Kalshi Volume Reaches $18.37B, Up 17.28% for Sept. 28-Oct. 4

Kalshi handled $18.37 billion in volume from Sept. 28 through Oct. 4, up 17.28% from the previous UTC week. It was the highest of the seven weekly values reviewed for this report.

The largest measured increase was in Kalshi's identified Exotics category, which accounted for 64.34% of platform volume. Several of the leading individual markets were multi-leg sports combos.

Polymarket US reported $2.71 billion in volume for Sept. 28-Oct. 4 Business Dates, down 4.41% from the prior week. Polymarket's Sept. 28-Oct. 4 Eastern week recorded $519.01 million in dollar volume, up 6.26%.

Top-line performance notes

• Kalshi: Weekly volume reached $18.37 billion, up 17.28% from $15.66 billion the previous UTC week.

• Kalshi Exotics: The identified category reached $11.82 billion, up 24.87%, accounting for 64.34% of Kalshi's total volume.

• Sports: Kalshi's identified Sports-classified series generated $3.64 billion, up 1.31%.

• Football: Identified Football-tagged series generated $1.37 billion, up 7.20%.

• Financials: The identified category reached $83.25 million, up 646.26% from $11.16 million, a large percentage gain from a relatively small base.

• Crypto: The identified category reached $2.42 billion, up 7.37%. BTC-tagged series were the largest identified asset subset.

• Polymarket US: Weekly volume was $2.71 billion, down 4.41% from $2.83 billion for Sept. 21-27.

• Polymarket: Eastern-calendar dollar volume was $519.01 million, up 6.26% from $488.42 million.

Our prediction market volume tracker follows trading across the platforms. The reporting periods and dollar-volume conventions used here are explained below.

Kalshi's leading individual markets include multi-leg sports combos

The biggest story of the week was Kalshi's Exotics category.

The identified Exotics category reached $11.82 billion, up 24.87% from $9.47 billion. It accounted for 64.34% of all Kalshi volume and 86.95% of the platform's $2.71 billion weekly increase, using the same series mapping for both weeks.

The leading examples included multi-leg markets combining player statistics, game winners and point spreads. These individual markets show how combos feature among the leaders; the category-wide sports and leg mix is not measured here.

The week's largest individual market was a 10-leg NFL combo involving player statistics and team winners. It generated $117.16 million in volume.

The second-largest market was a 10-leg college football combo covering several games and point spreads. It generated $102.68 million.

Baseball also produced a large multi-leg market. A four-leg MLB player performance combo involving Matt Olson, Mookie Betts, Jonathan Aranda, and Manny Machado generated $36.19 million.

A combo is one market containing several conditions. Its reported volume is counted once at the parent-market level, regardless of the number of legs, and is not allocated to the underlying games or players.

Football-tagged series increased, with NFL outcome markets among the leaders

Kalshi's identified Sports category generated $3.64 billion, up 1.31% from the previous week.

Within that mapping, Football-tagged series accounted for $1.37 billion, up 7.20%. This covers the identified native tag rather than separate all-in NFL and college-football totals.

The Philadelphia-wins outcome market against Chicago was the largest individual NFL game outcome market in the reviewed ranking, at $50.67 million. The Pittsburgh-wins outcome against Cleveland generated $36.82 million. These figures measure individual outcomes, not whole-game totals.

Two outcomes from the Rams-Broncos matchup appeared separately among the leaders: the Rams-wins market generated $35.59 million and Denver-wins generated $32.50 million. Both figures count trading during the UTC reporting week, including trading in a market whose game took place earlier.

The identified Football-tagged series generated less volume than the Exotics category. The leading individual NFL outcome, at $50.67 million, generated less than half the volume of the largest individual combo, at $117.16 million.

For the game-by-game breakdown, see our NFL Week 4 data page.

Soccer jumped while baseball cooled

Football wasn't the only sports category moving on Kalshi.

Identified Soccer-tagged series increased 40.73% to $452.63 million.

Identified Baseball-tagged series fell 32.59% to $362.07 million. The reporting week followed the Sept. 27 end of the MLB regular season.

Crypto and financial markets gained volume

Financials posted a much larger percentage increase than the other sizable identified categories, although its $83.25 million remained far below Exotics, Sports and Crypto.

The identified Financials category jumped from $11.16 million to $83.25 million, a 646.26% increase.

Financials is Kalshi's series-category label. It is kept separate here from Economics and Commodities rather than merged into a broader finance total.

The identified Commodities category reached $274.64 million, up 24.38%.

Kalshi's identified Crypto category reached $2.42 billion, up 7.37%.

BTC-tagged series accounted for $2.13 billion, up 6.78%, including BTC-versus-ETH products.

ETH-tagged series generated $118.90 million, up 21.61%. BTC and ETH tags can overlap, so their rows are non-additive subsets of Crypto.

Among the mapped categories in this report, Crypto was the largest after Exotics and Sports. The asset-tag subsets cover only part of the Crypto total.

Smaller categories are growing quickly too

Several smaller identified categories posted large percentage gains.

The identified Science and Technology category increased 51.30% to $6.93 million.

The identified Economics category rose 47.16% to $19.34 million.

The identified Mentions category increased 31.34% to $9.80 million.

Kalshi has more than doubled in six weeks

The retained weekly series provides historical context. Earlier weekly figures are historical reporting snapshots.

Kalshi's weekly volume increased from $9.06 billion for the week ending Aug. 23 to $18.37 billion for the week ending Oct. 4. Using the unrounded values, that is a 102.65% increase over six weeks.

Our earlier report covered Kalshi's $15.27 billion week during that climb.

The reviewed Kalshi weekly values rose through late August and September. NFL, college football, and baseball combos feature among the leading individual markets in the latest week.

The historical week ending Sept. 27 recorded 88,115,678 trades. That execution count is separate from the volume figures above.

Polymarket US pulls back after its earlier growth; Polymarket rises

Polymarket US grew substantially from late August to late September before declining in the latest completed Business-Date week.

Polymarket US volume increased from the retained $876.42 million late-August benchmark to $2.83 billion for Sept. 21-27, a 223.22% increase using unrounded values. It then fell 4.41% to $2.71 billion for Sept. 28-Oct. 4. Polymarket's latest Eastern week rose 6.26% in dollar volume.

For the previous week's comparison, see our report on Polymarket US's growing share of tracked volume.

Reporting periods and methodology

The Sept. 28-Oct. 4 week crosses a quarter boundary: Q3 ended Sept. 30, and Q4 began Oct. 1. This report compares completed weeks, not full quarters.

Kalshi and Polymarket US figures use our $1 face-value volume convention; they are not cash spent. Polymarket figures measure execution-price dollar volume. Kalshi uses UTC weeks, Polymarket US uses official Business Dates, and Polymarket uses Eastern-calendar weeks, so the three rows are not added into an industry total.

Category and tag comparisons use one fixed Kalshi series mapping for both weeks. They cover identified series under the current labels, rather than a complete historical classification. Tags can overlap, and the Exotics category is kept separate from sport-specific tags.

The Kalshi category mapping leaves $1.14 million of current-week volume and $2.07 million of prior-week volume outside the identified categories. The comparison retains that remainder rather than assigning it to a sport or asset.

The key number heading into next week

Kalshi's $18.37 billion week and 17.28% increase are the clearest findings in this comparison. The next question is whether that higher level persists in subsequent completed UTC weeks.

The identified Exotics category is worth watching: it represented 64.34% of current-week Kalshi volume, and its 24.87% growth exceeded the identified Sports category's 1.31% increase.

Financials and Crypto also increased in the fixed series comparison. Those gains show more trading volume in the identified categories, without attributing that change to individual traders switching from sports.

Next week's comparison will track whether Kalshi sustains its higher volume, whether Polymarket US rebounds from its 4.41% decline, and whether Polymarket extends its 6.26% dollar-volume increase.