Why plan your pace instead of just calculating it
A pace calculator tells you that a 4-hour marathon is 5:41 per kilometre. Race day is never that tidy: it may be warm and humid, the course may be at altitude or exposed to wind, the start may be crowded, and your watch will almost certainly measure more than the official distance. This planner puts all of that into one plan, so the pace on your wrist is the pace that actually gets you to your goal.
The three strategies
Even pace
The same pace all the way. Most marathon world records have been run with close to even splits, and it is the simplest plan to follow.
Negative split
The second half 1–2 % faster than the first. It protects you against the most common mistake, starting too fast, and leaves something for the finish.
10-10-10
For the marathon: the first 10 miles slightly slower and easy, the next 10 at goal pace, the last 10K as fast as you can hold. The planner applies the same shape to any distance.
Crowded start
In big races the first kilometre or mile is often slower than planned. Planning for it stops you sprinting to “win the time back”.
Example: a 4-hour marathon, three ways
Elapsed time at each 5 km for a 4:00:00 goal in good conditions. All three finish in exactly four hours.
| Checkpoint | Even | Negative split 2 % | 10-10-10 |
|---|---|---|---|
| 5 km | 28:26 | 28:43 | 29:00 |
| 10 km | 56:53 | 57:27 | 58:00 |
| 15 km | 1:25:19 | 1:26:10 | 1:26:59 |
| 20 km | 1:53:45 | 1:54:54 | 1:55:32 |
| Half | 2:00:00 | 2:01:12 | 2:01:47 |
| 25 km | 2:22:12 | 2:23:10 | 2:23:58 |
| 30 km | 2:50:38 | 2:51:20 | 2:52:23 |
| 35 km | 3:19:05 | 3:19:29 | 3:20:19 |
| 40 km | 3:47:31 | 3:47:38 | 3:47:54 |
| Finish | 4:00:00 | 4:00:00 | 4:00:00 |
How the conditions are worked out
- Heat and humidity: the temperature-plus-dew-point rule (both in °F) used by many coaches: no change at 100 or below, about 1–2 % at 121–130, 3–4.5 % at 141–150, and no hard racing above 180. Details in the heat pace calculator.
- Altitude: about 1.2 % slower per 1,000 ft above 3,000 ft when acclimatised (Daniels), or the larger drop measured in sea-level athletes on arrival (about 6.3 % of VO2max per 1,000 m above 300 m, Wehrlin & Hallén 2006). See the altitude pace calculator.
- Wind: a physics model of air resistance at equal effort (Pugh 1971; da Silva 2022). A headwind costs more than the same tailwind gives back, so even a loop course is slower on a windy day. Forecast wind is reduced to the speed at running height. See the wind pace calculator.
Why your watch needs a faster pace
Certified road courses are measured along the shortest route a runner could take, plus a tiny safety margin, so they are never short. Real runners weave around others, take wide corners and pick up GPS error, and typically log 0.5–1.5 % more than the official distance. At 1 %, a marathon becomes about 42.6 km on your watch. If you hold your goal pace by the watch, you finish roughly 2½ minutes behind your goal. The watch pace column corrects for that, and the elapsed times at each marker remain your true checkpoints.
Use the elapsed times, not just the pace. Course markers are measured correctly; your watch is not. Check your elapsed time at each kilometre or mile marker against the pace band, and adjust gradually rather than all at once.
- Daniels J. Daniels' Running Formula (altitude adjustment guidance).
- Wehrlin JP, Hallén J (2006). Linear decrease in VO2max and performance with increasing altitude in endurance athletes. European Journal of Applied Physiology 96: 404–412.
- Pugh LGCE (1971). The influence of wind resistance in running and walking and the mechanical efficiency of work against horizontal or vertical forces. Journal of Physiology 213: 255–276.
- Daniels J, Gilbert J (1979). Oxygen Power (VDOT equivalent times).
Last reviewed: September 2026 · Health disclaimer