Your equivalent time at another distance
From one recent result we estimate what you could do at any other distance. And we tell you when not to trust it.
Your figures
Result
- For
- Half marathon
- At a pace of
- 5:14 /km
- Your current pace
- 5:00 /km
- Pace difference (s/km)
- 14
What you would run at every distance
| Distance | Time | Pace |
|---|---|---|
| 1,000 m | 4:21 | 4:21 /km |
| Mile | 7:13 | 4:29 /km |
| 3,000 m | 13:57 | 4:39 /km |
| 5K | 23:59 | 4:48 /km |
| 10K | 50:00 | 5:00 /km |
| 15K | 1:16:51 | 5:07 /km |
| Half marathon | 1:50:19 | 5:14 /km |
| Marathon | 3:50:01 | 5:27 /km |
What we assume
- Uses Riegel with the standard exponent of 1.06, which is the usual choice for road running.
- It assumes you have trained for the target distance. The formula knows nothing about your long runs.
- It gets optimistic when the two distances are far apart, and the tool says so with the actual distances you picked.
How it is calculated
Riegel's formula relates a known time to a target distance:
T2 = T1 x (D2 / D1) ^ 1.06
The exponent is what matters. If it were 1, the prediction would keep your exact pace over any distance, which is obviously wrong: nobody runs a marathon at their 5K pace. The 1.06 encodes how much pace fades as distance grows.
Where it stops working
The further apart the two distances, the more the formula flatters you. Predicting a marathon from a 5K is the classic case: it produces a number that a well-trained runner might hit and that most people will not. The warning above names the distances you actually chose, so you know when you are in that territory.
What it cannot know
Endurance for the target distance. A marathon is not a long 10K; without the long runs behind you, no formula saves you from the wall at 32 km.
An example
A 10K in 50:00 predicts a half marathon of about 1:51, at 5:16 per kilometre against your current 5:00. Sixteen seconds per kilometre slower, which is roughly what the extra distance costs.
Frequently asked questions
How accurate is it?
Good between neighbouring distances (5K to 10K, 10K to half) if you have trained for the target. It gets steadily more optimistic as the gap widens.
Why does it predict a slower pace for a longer distance?
Because pace fades with distance. That is exactly what the 1.06 exponent captures; with an exponent of 1 the prediction would be a straight line and plainly wrong.
Can I use it the other way round, from long to short?
You can, and the tool warns you when you do. Predicting downwards undersells you: over short distances speed and technique matter more than endurance, and the formula does not know how fast you are.
Keep calculating
All tools →Updated on 2026-08-27. Calculations run in your browser; nothing you type is sent to a server.