Kalshi’s 15-minute Bitcoin contracts drove 95% of crypto growth in September

Kalshi recorded a large increase in crypto notional volume in September 2026 driven by its 15-minute Bitcoin contracts: those contracts added an extra $1.245bn between August and September and accounted for 95.3% of the platform’s net crypto volume increase over that period. The figure is part of a broader shift in which 15-minute series, in Bitcoin and eight other references, concentrated most growth while several longer-duration products lost activity.

## How 15-minute contracts work and what the "notional volume" measures

15-minute contracts let traders bet on whether an asset’s reference price will close the 15-minute window at or above a specified target. The "notional volume" counts each contract at a face value of $1 regardless of the price paid. That metric captures trading intensity — including repeated turnover — and does not reflect customer deposits, actual spend, or platform revenue.

## 15-minute Bitcoin contracts: detailed growth figures

Kalshi’s crypto notional volume rose by 17.2%, from $7.58bn in August to $8.89bn in September 2026. The 15-minute Bitcoin series grew 22.6%, from $5.51bn to $6.75bn; that increase of $1.245bn explained nearly all of the crypto category’s net gain of $1.306bn. In September the 15-minute Bitcoin contracts made up 75.9% of crypto volume, up from 72.6% in August.

Collectively, the nine assets with 15-minute series generated $7.63bn in September, a rise of 22.5% from $6.23bn in August. The combined share of those series in crypto volume increased from 82.1% to 85.8%. The aggregated $1.40bn growth of those series exceeded the category’s net increase because crypto markets outside those nine instruments lost a total of $95.9m.

All other Bitcoin formats fell by roughly 6.1%, from $1.26bn to $1.18bn. Within those formats, contracts that bet Bitcoin would finish above specific thresholds declined 6.5%, from $1.22bn to $1.14bn.

The second half of September showed higher activity: the 15-minute Bitcoin series produced $3.74bn between 16–30 September, 24.4% more than the $3.01bn from 1–15 September. Total crypto volume across the two halves rose 21.4%.

## Performance of 15-minute series in altcoins

Non‑Bitcoin crypto volume rose about 16.9% across all durations. Among 15-minute products, Ethereum, XRP and Solana gained share while HYPE and BNB declined. Several assets posted notable absolute increases: Zcash and NEAR more than doubled their volume to $47.4m and $37.4m respectively. These results show the 15-minute format’s growth was not uniform across assets.

## Commodities: seven 15-minute series dominate and gold drives two-thirds of the gain

Kalshi’s commodities notional volume rose 117.3%, from $410.2m in August to $891.3m in September 2026. Seven 15-minute series produced $864.9m in September. Gold led with $541.6m, followed by WTI at $137.8m and silver at $105.4m; gold and silver together accounted for 72.6% of the category total.

Kalshi launched its 15-minute gold and silver markets in August. In September gold volume climbed 149.5% and silver 47.4%. Gold added $324.5m and contributed 67.5% of the commodities net increase, raising its share from 52.9% in August to 60.8% in September.

Other metals and energy made smaller contributions: copper $38.8m, natural gas $29.5m, palladium $6.1m and platinum $5.7m.

## Longer-duration products lost ground while 15-minute contracts concentrated the market

Products outside the seven 15-minute series fell 33.1%, from $39.5m in August to $26.4m in September. The 15-minute series increased their commodity market share from 90.4% to 97.0% between the months. Several longer-duration products saw steep declines: hourly gold fell 75.2% (from $7.3m to $1.8m) and hourly silver dropped 85.8% to roughly $517,000. Daily gold markets declined from $3.0m to $1.8m. The lone exception was the weekly natural gas market, which rose from about $150,000 to $836,000, though its volume remained marginal compared with the $29.5m traded in the 15-minute gas series.

## Competition and volume distribution: Polymarket US and Coinbase

Polymarket US introduced its 15-minute Bitcoin markets on 22 September; between 22 and 30 September those markets generated $117.1m in notional volume. In the same interval Kalshi’s equivalent series produced $2.29bn, about 19.5 times more.

Activity on Polymarket US trended up toward month‑end: from 28–30 September it contributed $71.4m, 61.0% of its nine‑day total. Polymarket US’s average daily volume rose from $7.6m (22–27 Sept.) to $23.8m (28–30 Sept.). That acceleration indicates rising demand during the launch window, although nine days are not enough to prove sustainability.

In both markets the format dominated the crypto category: on Polymarket US 15-minute Bitcoin contracts represented 89.5% of crypto volume in September, versus 75.9% on Kalshi.

Coinbase, for its part, published on 6 October 2026 an announcement highlighting the crypto 15-minute markets operated by Kalshi, expanding access to those contracts from its platform. That step broadens distribution of Kalshi’s products to Coinbase users.

## What to watch next

The TickerTracker data used for this analysis cover 1–31 August and 1–30 September 2026. The concentration of growth in 15-minute series — notably Bitcoin and gold within commodities — is the immediate takeaway. For providers and operators interested in these formats, priorities are to watch whether demand holds in October and whether entrants such as Polymarket US and distribution through Coinbase change market share. For further reading on markets and platforms, see our pieces in [B2B coverage](/b2b) and in [regulation section](/regulation).