Pick a goal. Plan the splits.
Set your target marathon time and how aggressively you want to negative-split. We hand back the first/second half plan and every-5K target.
For a 4:00:00 marathon with a -2% negative, run the first half in 2:01:13 and the second in 1:58:47.
Cumulative time at each 5K mark. Print this and stick it on your wrist on race day.
| Distance | Target pace | Cumulative |
|---|---|---|
| 5K | 5:45/km | 28:44 |
| 10K | 5:45/km | 57:27 |
| 15K | 5:45/km | 1:26:11 |
| 20K | 5:45/km | 1:54:54 |
| 25K | 5:38/km | 2:23:11 |
| 30K | 5:38/km | 2:51:20 |
| 35K | 5:38/km | 3:19:29 |
| 40K | 5:38/km | 3:47:38 |
| Marathon | 5:38/km | 4:00:00 |
Almost every world record at the marathon distance was set with an even or slightly negative split. Going out too fast — even by 5-10 seconds per km — costs disproportionately more in the back half. A controlled first 21 km lets you spend energy where it matters: the closing 10K.
On race day, hit the 5K splits in the table — not by 30 seconds, not 30 seconds slow. The first 5K should feel almost too easy. Aim for the half-marathon split (21.1K) within 5-10 seconds of the planner. If you arrive there fresh, the back half plan is in reach.
Running the second half of a race faster than the first. A 2% negative split on a 4-hour marathon means about 2:01 first half, 1:59 second half.
Yes, with discipline. Most amateurs positive-split because they go out on adrenaline. A 1-2% negative split is a reasonable goal if you’ve trained at marathon pace and pace yourself in the first 10K.
Start with -1% if you’re unsure. -2% is the classic goal for a well-paced marathon. -3% requires excellent fitness and discipline — most runners overcook the first half trying for it.
No — memorize the half-marathon target and check 5K splits as cues. If you’re consistently 30+ seconds off the plan, adjust before halfway. Don’t spend the second half doing math.