Upcoming 100Ks

Endurance Grid lists thirty 100Ks across the US, from September 2026 to November 2027 across 18 states.

30
Races
18
States

What a 100K is

A 100K is a running race where athletes run 62.1 miles long (100 kilometers) for time.

100Ks are busiest in October and June, with the most in Connecticut, Colorado, Indiana, and Wisconsin.

Frequently Asked Questions

How many 100K ultramarathons are there in the US?
Endurance Grid's Race Calendar lists 30 upcoming 100K ultramarathons across 18 states.
How far is a 100K ultramarathon?
A 100K is a running race where athletes run 62.1 miles long (100 kilometers) for time.
Which states have the most 100K ultramarathons?
The states with the most 100K ultramarathons on Endurance Grid's Race Calendar are Connecticut, Colorado, Indiana, Wisconsin, Florida, and Pennsylvania.