3:45 Marathon Pace: 8:35/mi (5:20/km)
A 3:45 marathon is 8:35 per mile, or 5:20 per kilometer, held for 26.2 miles (42.195 km). Halfway comes at 1:52:30. Below: splits for three pacing strategies, what your recent races say about this goal, and a plan built for it.
3:45 marathon splits: even, negative and positive
Even pacing holds the same pace from the first mile to the last. A negative split runs the first half at 51 % of the goal time and the second half at 49 %, so you finish faster than you started. A positive split (49/51) banks a small cushion early and gives it back later; it is the most common way to run a race and the hardest way to run it well. The finish time is the same in all three columns, only the cumulative time at each mark changes.
| Mile | Even | Negative split 51/49 | Positive split 49/51 |
|---|---|---|---|
| 1 | 8:35 | 8:45 | 8:25 |
| 2 | 17:10 | 17:30 | 16:49 |
| 3 | 25:45 | 26:16 | 25:14 |
| 4 | 34:20 | 35:01 | 33:38 |
| 5 | 42:54 | 43:46 | 42:03 |
| 6 | 51:29 | 52:31 | 50:28 |
| 7 | 1:00:04 | 1:01:16 | 58:52 |
| 8 | 1:08:39 | 1:10:02 | 1:07:17 |
| 9 | 1:17:14 | 1:18:47 | 1:15:41 |
| 10 | 1:25:49 | 1:27:32 | 1:24:06 |
| 11 | 1:34:24 | 1:36:17 | 1:32:31 |
| 12 | 1:42:59 | 1:45:02 | 1:40:55 |
| 13 | 1:51:34 | 1:53:48 | 1:49:20 |
| Half | 1:52:30 | 1:54:45 | 1:50:15 |
| 14 | 2:00:09 | 2:02:14 | 1:58:03 |
| 15 | 2:08:43 | 2:10:39 | 2:06:48 |
| 16 | 2:17:18 | 2:19:04 | 2:15:33 |
| 17 | 2:25:53 | 2:27:28 | 2:24:18 |
| 18 | 2:34:28 | 2:35:53 | 2:33:04 |
| 19 | 2:43:03 | 2:44:17 | 2:41:49 |
| 20 | 2:51:38 | 2:52:42 | 2:50:34 |
| 21 | 3:00:13 | 3:01:07 | 2:59:19 |
| 22 | 3:08:48 | 3:09:31 | 3:08:04 |
| 23 | 3:17:23 | 3:17:56 | 3:16:50 |
| 24 | 3:25:58 | 3:26:20 | 3:25:35 |
| 25 | 3:34:32 | 3:34:45 | 3:34:20 |
| 26 | 3:43:07 | 3:43:10 | 3:43:05 |
| Finish | 3:45:00 | 3:45:00 | 3:45:00 |
| Km | Even | Negative split 51/49 | Positive split 49/51 |
|---|---|---|---|
| 1 | 5:20 | 5:26 | 5:14 |
| 2 | 10:40 | 10:53 | 10:27 |
| 3 | 16:00 | 16:19 | 15:41 |
| 4 | 21:20 | 21:45 | 20:54 |
| 5 | 26:40 | 27:12 | 26:08 |
| 6 | 32:00 | 32:38 | 31:21 |
| 7 | 37:20 | 38:04 | 36:35 |
| 8 | 42:40 | 43:31 | 41:48 |
| 9 | 47:59 | 48:57 | 47:02 |
| 10 | 53:19 | 54:23 | 52:15 |
| 11 | 58:39 | 59:50 | 57:29 |
| 12 | 1:03:59 | 1:05:16 | 1:02:43 |
| 13 | 1:09:19 | 1:10:42 | 1:07:56 |
| 14 | 1:14:39 | 1:16:09 | 1:13:10 |
| 15 | 1:19:59 | 1:21:35 | 1:18:23 |
| 16 | 1:25:19 | 1:27:01 | 1:23:37 |
| 17 | 1:30:39 | 1:32:28 | 1:28:50 |
| 18 | 1:35:59 | 1:37:54 | 1:34:04 |
| 19 | 1:41:19 | 1:43:20 | 1:39:17 |
| 20 | 1:46:39 | 1:48:47 | 1:44:31 |
| 21 | 1:51:59 | 1:54:13 | 1:49:44 |
| Half | 1:52:30 | 1:54:45 | 1:50:15 |
| 22 | 1:57:19 | 1:59:28 | 1:55:10 |
| 23 | 2:02:39 | 2:04:42 | 2:00:36 |
| 24 | 2:07:59 | 2:09:55 | 2:06:02 |
| 25 | 2:13:19 | 2:15:09 | 2:11:29 |
| 26 | 2:18:39 | 2:20:22 | 2:16:55 |
| 27 | 2:23:58 | 2:25:36 | 2:22:21 |
| 28 | 2:29:18 | 2:30:49 | 2:27:48 |
| 29 | 2:34:38 | 2:36:03 | 2:33:14 |
| 30 | 2:39:58 | 2:41:16 | 2:38:40 |
| 31 | 2:45:18 | 2:46:30 | 2:44:07 |
| 32 | 2:50:38 | 2:51:43 | 2:49:33 |
| 33 | 2:55:58 | 2:56:57 | 2:54:59 |
| 34 | 3:01:18 | 3:02:11 | 3:00:26 |
| 35 | 3:06:38 | 3:07:24 | 3:05:52 |
| 36 | 3:11:58 | 3:12:38 | 3:11:18 |
| 37 | 3:17:18 | 3:17:51 | 3:16:45 |
| 38 | 3:22:38 | 3:23:05 | 3:22:11 |
| 39 | 3:27:58 | 3:28:18 | 3:27:37 |
| 40 | 3:33:18 | 3:33:32 | 3:33:04 |
| 41 | 3:38:38 | 3:38:45 | 3:38:30 |
| 42 | 3:43:58 | 3:43:59 | 3:43:56 |
| Finish | 3:45:00 | 3:45:00 | 3:45:00 |
Are you ready for a 3:45 marathon?
The Riegel formula (T2 = T1 × (D2 ÷ D1)1.06) links race times across distances. Recent results around these mark you as fit for a marathon in 3:45:
| Recent race | Time that predicts 3:45 | Pace |
|---|---|---|
| Half Marathon | 1:47:55 | 8:14/mi · 5:07/km |
| 10K | 48:55 | 7:52/mi · 4:53/km |
| 5K | 23:28 | 7:33/mi · 4:42/km |
Predictions from a 5K or 10K to the marathon assume marathon-specific mileage and long runs; without them the real result is slower than the formula. A recent half marathon is the most reliable guide.
Check your own numbers in the pace calculator, or let the generator use a recent race for training paces.
Build a free 3:45 marathon plan
Same engine as every plan on this site, but with your race date, your run days and your longest recent run. Prints to PDF, exports to your calendar. No signup.
Frequently asked questions
What pace is a 3:45 marathon?
8:35 per mile, or 5:20 per kilometer, for the full 26.2 miles. Running even splits you pass halfway at 1:52:30.
What is the halfway split for a 3:45 marathon?
1:52:30 with even pacing, 1:54:45 with a negative split (51/49), 1:50:15 with a positive split (49/51).
What Half Marathon, 10K, 5K time predicts a 3:45 marathon?
Half Marathon in about 1:47:55, 10K in about 48:55, 5K in about 23:28 (Riegel formula, exponent 1.06).
How many weeks do I need to train for a 3:45 marathon?
The generator builds marathon plans from 12 to 24 weeks and defaults to 16; it counts back from your race date. Enter 3:45 as the goal time and the plan sets easy, long and tempo paces from it.
Should I run a 3:45 marathon with even or negative splits?
Even or slightly negative. Both start conservatively; a negative split means your second half is faster, which is how most personal bests are run. A positive split spends energy early and is the usual cause of a slow last quarter.