5K to 10K Time Conversion: What 10K Can You Run?

Here is the quick answer. Your 10K time is about 2.08 times your 5K time. So a 20:00 5K points to about a 41:36 10K. A 25:00 5K points to about 52:00. Your 10K pace will be roughly 8 to 13 seconds per kilometer slower than your 5K pace. The longer race is not much slower per km — but you hold that pace for twice as long.

The table below converts common 5K times into a 10K time and a 10K pace. Find the row closest to your 5K.

Your 5K	Projected 10K	10K pace /km
18:00	37:26	3:44
20:00	41:36	4:09
22:00	45:45	4:34
25:00	52:00	5:11
28:00	58:14	5:49

What 10K time can I run off my 5K?

Take your 5K time and multiply it by about 2.08. That gives a fair 10K guess for most runners.

Why not just double it? Because the longer you run, the more you slow down. If you simply doubled your 5K, you would expect to hold your exact 5K speed for 10 kilometers. Almost no one can. So the real 10K is a little more than double.

The 5K is also a great place to start a prediction. A short race like the 5K is close in distance to the 10K. When the gap between two races is small, the guess is very accurate (RunnersConnect, 2024). Your 5K predicts your 10K far better than it predicts your marathon.

How much slower is 10K pace than 5K pace?

Your pace drops by about 4 to 5% each time the race distance doubles (MarathonGuide, race predictor). Going from 5K to 10K is one doubling. So your 10K pace is about 4 to 5% slower than your 5K pace.

In real numbers, that is about 8 to 13 seconds per kilometer. Here is how that looks:

• A 20:00 5K is 4:00 per km. The 10K is about 4:09 per km — 9 seconds slower.
• A 25:00 5K is 5:00 per km. The 10K is about 5:11 per km — 11 seconds slower.
• A 28:00 5K is 5:36 per km. The 10K is about 5:49 per km — 13 seconds slower.

Slower runners lose a few more seconds per km. That is normal. The percentage stays about the same; the seconds just add up faster at a slower pace.

This slowdown is not random. Scientists call it a "fatigue factor." It measures how much your speed drops as the race gets longer, and it is steady enough to predict (Vickers & Vertosick, 2016).

What does it take to hold 10K pace?

The 10K asks more of your aerobic engine than the 5K does. The 5K is fast and short. The 10K is almost as fast but lasts twice as long. That extra time is where runners fade.

Three things help you hold the pace to the line:

1. Weekly miles. More easy running builds the engine that carries you through the back half. A common intermediate 10K plan has runners going five to six days a week, around 15 to 25 miles (Hal Higdon, 10K intermediate).

2. One tempo run a week. A steady, "comfortably hard" run for 20 to 30 minutes teaches your body to clear fatigue at close to 10K pace. This is the single best workout for the 10K.

3. A weekly long run. Even a 60 to 90 minute easy long run makes 10K race pace feel easier. It is the cheapest way to stop the late-race fade.

If your training is mostly short, fast runs, you will likely finish near the slow end of the prediction. Add miles and a tempo run, and you move toward the fast end.

How do I predict my 10K?

Enter your most recent 5K and let PIRX do the math. You will get a projected 10K time and the pace to practice — free, no signup, no watch.

PIRX's proprietary machine-learning prediction engine learns your style instead of using one fixed formula. It shows a supported range, not a fake-exact number, so you know how sure it is. Add a second race, like a recent 10K or a longer run, and the range gets tighter.

This is what makes PIRX different. Strava tells you what you did. Garmin shows your data. PIRX tells you why it happened and what's next — with validated prediction accuracy of 98% across PIRX users.

New here? Start with the complete guide to predicting your race time. Want a longer goal next? See what marathon you can run off your half, or check your speed with the 5K Time Predictor. When you are ready, project your 10K below.

Sources

• Vickers, A.J. & Vertosick, E.A. (2016). An empirical study of race times in recreational endurance runners. BMC Sports Science, Medicine and Rehabilitation. (2,303 recreational runners; the "fatigue factor" k.)
• MarathonGuide.com. Race results predictor. (Pace decreases ~4–5% as race distance doubles.)
• RunnersConnect (2024). How accurate are race calculators? (Predictions are most accurate when the distance gap is small.)
• Hal Higdon. Intermediate 10K training program.