Racing smarter
What pace is a 3:45 marathon?
3:45:00 for the marathon is 5:20/km (8:35/mi), held the whole way. Halfway on even pace is 1:52:30. Most watches measure the course long, so the pace you actually need on the screen is nearer 5:15/km.
| What | Number | The qualifier |
|---|---|---|
| Pace needed | 5:20/km (8:35/mi) | even, start to finish |
| Halfway (even) | 1:52:30 | 1:54:45 on a 2% negative split |
| Watch pace at 1.5% overage | 5:15/km (8:27/mi) | what the screen has to show |
| Distance | 42.195 km (26.22 mi) | the measured course, not the watch |
What pace is a 3:45 marathon?
3:45:00 over 42.195 km (26.22 mi) is 5:20/km (8:35/mi), held from the first step to the last. There is no rounding slack in that number: run the first kilometre at 5:30/km and you have already spent ten seconds you will not get back cheaply.
3:45 sits in an awkward gap. It is too fast to treat as a survival run and too slow to be a speed problem, so it is almost entirely an endurance and pacing question. Most people who run it train four to five days a week at 45 to 60 km. The pace is 5:20/km (8:34/mi), which is close enough to many runners' comfortable long-run pace that it feels wrong in a good way for the first hour. That is the trap. A 3:45 attempt is usually lost between 28 and 34 km, and it is lost by two minutes of enthusiasm in the first hour. Run the first 10 km 10 seconds a kilometre slower than goal and you will pass people all afternoon.
What the splits look like
| Kilometre | Split | Elapsed |
|---|---|---|
| 1 | 5:20 | 5:20 |
| 5 | 5:20 | 26:40 |
| 10 | 5:20 | 53:19 |
| 15 | 5:20 | 1:19:59 |
| 20 | 5:20 | 1:46:39 |
| 25 | 5:20 | 2:13:19 |
| 30 | 5:20 | 2:39:58 |
| 35 | 5:20 | 3:06:38 |
| 40 | 5:20 | 3:33:18 |
| 42.195 | 1:02 | 3:45:00 |
And in miles, for a course measured that way:
| Mile | Split | Elapsed |
|---|---|---|
| 1 | 8:35 | 8:35 |
| 3 | 8:35 | 25:45 |
| 6 | 8:35 | 51:29 |
| 9 | 8:35 | 1:17:14 |
| 12 | 8:35 | 1:42:59 |
| 15 | 8:35 | 2:08:43 |
| 18 | 8:35 | 2:34:28 |
| 21 | 8:35 | 3:00:13 |
| 24 | 8:35 | 3:25:58 |
| 26.22 | 1:53 | 3:45:00 |
Where should I be at halfway?
Even pace puts you through halfway at 1:52:30. Most people who finish this time went through slightly slower than that, not faster — a 2% negative split means halfway at 1:54:45 and a second half of 1:50:15.
The decision rule for race day: if you reach halfway more than 2:15 ahead of 1:52:30, you are not ahead of schedule, you are borrowing. Ease back to 5:20/km (8:35/mi) and hold it.
What if my watch measures the course long?
Almost every watch does. A marathon that reads 1.5% long on your wrist means you have to run 5:15/km by the watch to finish in 3:45:00 by the clock. That is the pace to put on the screen, and it is why pacing off a watch's average-pace field alone tends to leave people a minute or two short.
Questions runners actually ask
- Is a 3:45 marathon a good time?
- Good is a comparison, and it depends who with. Whether it is achievable for you is the answerable question: it comes down to a recent race, your weekly volume and your longest run. The race predictor puts numbers on all three.
- Should I run even splits or negative splits?
- Even, planned; slightly negative, executed. Going through halfway 1-2% slower than even pace costs almost nothing if you are strong at the end, and saves the race if you are not.
Sources
- Hanley B et al. Pacing profiles of senior athletes at the World Athletics Championships. Front Sports Act Living 4:964905, 2022 primary
- Deaner RO et al. Men are more likely than women to slow in the marathon. Med Sci Sports Exerc 47(3):607-616, 2015 primary
- World Athletics Competition Rules, Book C2.1 — course measurement and the short course prevention factor reference
Changelog
- — First published.