Colfax Marathon: Pacing & Race-Day Strategy
Denver’s only marathon: flat and fast on paper, but run a mile above sea level.
- 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
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 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 |
Grade adjustment is a model, not a promise. It assumes even effort and ignores wind, heat, and how well your legs handle sustained descent — which on a steep course is often the deciding factor.
Plan your mile splits
Enter your goal time to get a mile-by-mile pacing band for Colfax Marathon. The even pace option is pre-selected to suit this course.
| Mile | Pace | Elapsed |
|---|---|---|
| 1 | 9:09/mi | 9:09 |
| 2 | 9:09/mi | 18:18 |
| 3 | 9:09/mi | 27:28 |
| 4 | 9:09/mi | 36:37 |
| 5 | 9:09/mi | 45:46 |
| 6 | 9:09/mi | 54:55 |
| 7 | 9:09/mi | 1:04:05 |
| 8 | 9:09/mi | 1:13:14 |
| 9 | 9:09/mi | 1:22:23 |
| 10 | 9:09/mi | 1:31:32 |
| 11 | 9:09/mi | 1:40:41 |
| 12 | 9:09/mi | 1:49:51 |
| 13 | 9:09/mi | 1:59:00 |
| 14 | 9:09/mi | 2:08:09 |
| 15 | 9:09/mi | 2:17:18 |
| 16 | 9:09/mi | 2:26:28 |
| 17 | 9:09/mi | 2:35:37 |
| 18 | 9:09/mi | 2:44:46 |
| 19 | 9:09/mi | 2:53:55 |
| 20 | 9:09/mi | 3:03:05 |
| 21 | 9:09/mi | 3:12:14 |
| 22 | 9:09/mi | 3:21:23 |
| 23 | 9:09/mi | 3:30:32 |
| 24 | 9:09/mi | 3:39:41 |
| 25 | 9:09/mi | 3:48:51 |
| 26 | 9:09/mi | 3:58:00 |
| 26.22 | 9:09/mi | 4:00:00 |
Fueling & 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.
Is 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.
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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