Type the digits in a row: 14530 means 1:45:30. The + and − buttons change the number by one step.Arrow keys ↑↓ change it by one step, with Shift by ten, and you can drag the number with the mouse.
10K: finish 50:00, pace 5:00 per kilometer, 12.0 kilometers per hour
Equivalent results by the Riegel formula
Even-pace splits every kilometer
- 1 km5:00
- 2 km10:00
- 3 km15:00
- 4 km20:00
- 5 km25:00
- 6 km30:00
- 7 km35:00
- 8 km40:00
- 9 km45:00
- 10 km50:00
Running pace is the minutes and seconds you spend on one kilometer. A 10K in 50 minutes is a pace of 5:00, a half marathon in 2 hours is 5:41, a marathon in 3:30 is 4:58.
The calculator rounds pace down to the whole second, because that is your target pace. A 3:30:00 marathon needs 4:58.6 per kilometer; at 4:59 you would finish in 3:30:16, 16 seconds over your goal.
How pace is calculated
Pace is time divided by distance: 50 minutes over 10 km gives 5 minutes per kilometer. Speed in km/h is the inverse: 60 minutes divided by pace in minutes. A pace of 6:00 is 10 km/h, 5:00 is 12 km/h, 4:00 is 15 km/h.
The calculator uses the official distances: 21.0975 km for the half marathon and 42.195 km for the marathon. With round 21 and 42 km, a marathon at 6:00 pace would end more than a minute earlier than it really does.
Finish time prediction with the Riegel formula
Predictions for other distances use Peter Riegel's formula: the time over a new distance equals the known time multiplied by the ratio of distances to the power of 1.06. From a 50-minute 10K it gives about 1:50 for the half marathon and 3:50 for the marathon.
It predicts speed, not readiness. The formula assumes you are trained for the longer distance, with long runs and enough weekly volume. Without that, a marathon prediction from a fast 5K is too optimistic. How to turn a prediction into a realistic goal, and why three scenarios beat one, is in the guide to choosing a race goal. Another way to predict is from VO2max: see VO2max: what it is, norms and how to raise it.
Pace chart: 5K, 10K, half marathon and marathon times
For a quick estimate without the calculator, find your pace in the table. Times use the official distances and are rounded to the second.
| Pace, min/km | Speed, km/h | 5K | 10K | Half marathon | Marathon |
|---|---|---|---|---|---|
| 3:30 | 17.1 | 17:30 | 35:00 | 1:13:50 | 2:27:41 |
| 3:45 | 16.0 | 18:45 | 37:30 | 1:19:07 | 2:38:14 |
| 4:00 | 15.0 | 20:00 | 40:00 | 1:24:23 | 2:48:47 |
| 4:15 | 14.1 | 21:15 | 42:30 | 1:29:40 | 2:59:20 |
| 4:30 | 13.3 | 22:30 | 45:00 | 1:34:56 | 3:09:53 |
| 4:45 | 12.6 | 23:45 | 47:30 | 1:40:13 | 3:20:26 |
| 5:00 | 12.0 | 25:00 | 50:00 | 1:45:29 | 3:30:59 |
| 5:15 | 11.4 | 26:15 | 52:30 | 1:50:46 | 3:41:31 |
| 5:30 | 10.9 | 27:30 | 55:00 | 1:56:02 | 3:52:04 |
| 5:45 | 10.4 | 28:45 | 57:30 | 2:01:19 | 4:02:37 |
| 6:00 | 10.0 | 30:00 | 1:00:00 | 2:06:35 | 4:13:10 |
| 6:15 | 9.6 | 31:15 | 1:02:30 | 2:11:52 | 4:23:43 |
| 6:30 | 9.2 | 32:30 | 1:05:00 | 2:17:08 | 4:34:16 |
| 6:45 | 8.9 | 33:45 | 1:07:30 | 2:22:24 | 4:44:49 |
| 7:00 | 8.6 | 35:00 | 1:10:00 | 2:27:41 | 4:55:22 |
| 7:15 | 8.3 | 36:15 | 1:12:30 | 2:32:57 | 5:05:55 |
| 7:30 | 8.0 | 37:30 | 1:15:00 | 2:38:14 | 5:16:28 |
| 7:45 | 7.7 | 38:45 | 1:17:30 | 2:43:30 | 5:27:01 |
| 8:00 | 7.5 | 40:00 | 1:20:00 | 2:48:47 | 5:37:34 |
Average finish times and goal paces for the half and full marathon are in how long it takes to run a marathon, and for shorter races in the pages about 5K times and 10K times.
Pace in training and on race day
Your race pace is not the pace of every run. Most training is much slower: Hal Higdon advises running long runs at a conversational pace, where you can still talk to a partner, and writes that there is no such thing as too slow for them. Even in plans with intervals and tempo runs, fast work is the smaller part of the week.
So take two things from the calculator: your target race pace, for tempo work and your race splits, and a sense of how realistic it is given a recent result. How a training week is built is in the half marathon training guide and the race guides for 2027.
Quick answers
What pace do I need for a 50-minute 10K?
5:00 per kilometer, or 12 km/h. For one hour it is 6:00 per kilometer and 10 km/h, which lands exactly on the hour: for a margin, run slightly faster.
What pace do I need for a sub-2 half marathon?
5:41 per kilometer or faster: 2 hours over 21.0975 km is 5:41.3, and at 5:41 you finish in 1:59:54.
What pace do I need for a 4-hour marathon?
5:41 per kilometer. For 3:30 it is 4:58, for 3 hours 4:15: at 4:59 and 4:16 you would finish a few seconds over the goal.
How do I convert pace to speed?
Divide 60 by your pace in minutes. A pace of 5:30 is 5.5 minutes, and 60 ÷ 5.5 ≈ 10.9 km/h.
How accurate is the marathon prediction?
The Riegel formula shows what your speed allows if your endurance is trained. The bigger the gap between distances and the fewer long runs you have done, the more optimistic the prediction.
Train for your time
The calculator works from one result. Pacero builds a plan for your race and goal time, checks your finish forecast against your runs and updates the plan as you train.
Train with Pacero →First 7 days free, no card needed.Sources
- Peter Riegel, 1981: the time prediction formula.
- World Athletics, Competition Rules: marathon length of 42.195 km.
- Hal Higdon: Marathon Novice 1: long run pace.