Denver Colfax Marathon: Pacing & Race-Day Strategy
Denver’s only marathon: flat and fast on paper, but run a mile above sea level.
Last updated
- Where:
- Denver, Colorado
- When:
- Sunday, May 16, 2027
- Course:
- Flat · high altitude · loop
- Best run as:
- Even pace
Course & elevation
Colfax is essentially flat, with only gentle rolling grade through the city and barely any net change. The catch is altitude: the entire course sits around 5,300 feet, where the thinner air makes any pace feel noticeably harder. The layout is runnable, but the elevation is what defines the day.
- Start → Finish
- 5,300 → 5,300 ft
- Net
- +0 ft
- Total gain
- ≈ 400 ft
The certified route
Loop through Denver starting and finishing in City Park by Ferril Lake. The course runs out and back on Colfax Ave with a loop around Sloan Lake, a turnaround at Glen Ayre, a loop around the football stadium, and stretches on the Cherry Creek and South Platte River paths.
- Start
- On the road inside City Park, 45 ft east of the southwest corner of the island on the east side of Thatcher Fountain, 78 ft east of LP 4898 on the south side of the road at the corner.
- Finish
- On the City Park roadway just east of the pavilion parking lot, on the east side of Ferril Lake, 45 ft north of the manhole on the east side of the road.
Underfoot
Almost entirely paved, with about 1 percent on a track.
Through, in order
Denver
What you pass
- Miles 8 to 11: loop around Sloan Lake on the walking path
- Miles 20 to 22: loop around the football stadium
- Miles 22 to 25: the Cherry Creek and South Platte River paths
Worth knowing
- On Colfax Ave, outbound runners use the north-side westbound lane and inbound runners run east in the same lane.
- On the Cherry Creek Path runners stay in the east-side pedestrian lanes, both outbound and inbound.
Transcribed from the USATF certificate for Denver Colfax Marathon (CO23001DT), measured 6 and 7 April 2023. Where the certificate is silent, so are we.
Key moments
- Mile 0 & 26.2Start and finish in City Park near Ferril Lake.
- Mile 6.5Run through the Empower Field at Mile High stadium, a signature stretch.
- Mile 7–10Flat loop past Sloan’s Lake on the west side.
- Mile 20Second pass by the stadium before the trail run-in to City Park.
Pacing strategy
Respect the altitude. At 5,300 feet there’s roughly 17% less oxygen, so set goal pace honestly rather than chasing a sea-level PR. The terrain is flat enough for even pacing; run the early miles conservatively and let the thin air, not the course, be the limiter.
Pacing by goal time
Checkpoint splits for four common goals at Denver Colfax Marathon. These are effort-even rather than pace-even: the paces shift with the course profile, so climbs are slower and descents faster by the amount the grade actually costs. For any other goal time, use the planner below.
| Checkpoint | Sub-3:00 | Sub-3:30 | Sub-4:00 | Sub-4:30 |
|---|---|---|---|---|
| Mile 3.1 | 20:406:40/mi | 24:077:46/mi | 27:338:53/mi | 31:009:60/mi |
| Mile 6.2 | 41:367:09/mi | 48:328:20/mi | 55:289:32/mi | 1:02:2410:43/mi |
| Mile 9.3 | 1:02:017:09/mi | 1:12:218:20/mi | 1:22:419:32/mi | 1:33:0110:43/mi |
| Mile 12.4 | 1:22:256:35/mi | 1:36:107:41/mi | 1:49:548:47/mi | 2:03:389:53/mi |
| Mile 15.5 | 1:43:086:37/mi | 2:00:197:43/mi | 2:17:318:49/mi | 2:34:429:55/mi |
| Mile 18.6 | 2:03:507:07/mi | 2:24:288:18/mi | 2:45:079:29/mi | 3:05:4510:40/mi |
| Mile 21.7 | 2:24:217:01/mi | 2:48:258:11/mi | 3:12:289:21/mi | 3:36:3210:31/mi |
| Mile 24.9 | 2:44:536:41/mi | 3:12:227:48/mi | 3:39:508:55/mi | 4:07:1910:02/mi |
| Finish | 2:58:306:50/mi | 3:28:157:58/mi | 3:58:019:06/mi | 4:27:4610:14/mi |
Splits assume even effort and are adjusted for this course's climbs and descents, which cost more than they give back. A model, not a promise: wind and heat move real splits around. See how the pacing model works.
Plan your mile splits
Turn your goal time into a mile-by-mile plan for Denver Colfax Marathon, built from this course's elevation. The even pace approach comes pre-selected, and grade-adjusted pacing evens out your effort across the climbs and descents.
Plan Denver Colfax Marathon splitsFueling & hydration
Aid stations roughly every 1.5–2 miles with water and sports drink. Altitude and dry Colorado air accelerate dehydration, so drink early and consistently, and keep electrolytes coming.
Weather
Mid-May in Denver is usually cool at the start (around 40s°F) warming into the 60s, with strong high-altitude sun and typical spring variability.
What race morning has actually been like
The last 5 editions of Denver Colfax Marathon, measured at the start line rather than averaged across the month. Starts have run 33–53°F, averaging 47°F.
| Year | Date | Start | Dew pt | Wind | By late morning |
|---|---|---|---|---|---|
| 2021 | Oct 16 | 33°F | 23°F | 4 mph | 58°F |
| 2022 | May 15 | 53°F | 37°F | 7 mph | 69°F |
| 2023 | May 21 | 50°F | 44°F | 3 mph | 69°F |
| 2024 | May 19 | 51°F | 41°F | 4 mph | 76°F |
| 2025 | May 18 | 50°F | 44°F | 3 mph | 64°F |
The gap between the gun and late morning matters here. In 2021 it went from 33°F at the start to 58°F by late morning. A four-hour finisher ran a materially different race from a three-hour one.
Dates derived from the race's published pattern (3rd Sunday in May (2021 postponed to Saturday, October 16)), observations at Denver, Colorado (start). Source: Open-Meteo historical reanalysis (ERA5), 7-11am local at the start line. Reanalysis is modelled from station observations, so treat it as a close record rather than an official one. See how race-morning weather is built.
Is Denver Colfax Marathon a good Boston qualifier?
Yes. Start and finish sit at the same elevation, so no downhill adjustment applies and a time here is submitted as run.
This drop is our estimate rather than a figure from the course's certificate. If it sits near a threshold, confirm with the organizer.
Compare every course, how the downhill bands work, or work out your own target.
Dial in your pacing & fueling
New to how training builds toward a race like this? Start with Anatomy of a Running Plan, find your zones with the pace calculator, and plan race-day nutrition with the fueling calculator.
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