Polymarket US has traded $27.4B in 2026 through Oct. 15, with September its busiest month at $8.8B

September leads Polymarket US activity

Polymarket US has recorded $27.4B in trading volume in 2026 through Oct. 15, according to DeFi Rate’s venue tracker. September remains its busiest month, accounting for $8.8B of that total.

October volume so far stands at $5.7B, giving the venue an 11.1% share, according to DeFi Rate. For the week of Oct. 12, the tracker reports $1.15B in volume and a 10.8% share.

The tracker’s rolling-period figures show $11.6B in contracts traded over Sep 15-Oct 14, 2026. That represented 12% of prediction-market volume and an increase of 139% from the preceding 30 days.

DeFi Rate separately reports $3.3B in dollars paid for Sep 15-Oct 14, 2026. That measure is distinct from the $11.6B contract-volume figure, making the choice of metric important when comparing activity.

What it means for prediction markets

• The reporting window matters: The 10.8% weekly share, 11.1% October share and 12% rolling-period share describe different intervals, not directly comparable snapshots.
• Growth and market share measure different things: The 139% increase captures growth in Polymarket US contract volume against the preceding 30 days; the 12% figure measures its share of prediction-market volume.
• Volume is not an outcome forecast: These venue-level totals describe trading activity, rather than probabilities for individual contracts.