21:00 5K: what it equals and how to train for it
Running a 5K in 21:00 means holding 4:12 per kilometre (6:46 per mile). Here is what that fitness is worth at other distances, and the paces to train at.
Equal race times
Predictions from an equal-effort model: the time you could run at each distance with the same fitness and the right training. Longer distances need specific endurance work.
| Distance | Time | Pace per km | Pace per mile |
|---|---|---|---|
| 5K | 21:00 | 4:12 | 6:46 |
| 10K | 43:32 | 4:21 | 7:00 |
| 15K | 1:07:00 | 4:28 | 7:11 |
| 10 miles | 1:12:14 | 4:29 | 7:13 |
| Half marathon | 1:36:28 | 4:34 | 7:22 |
| Marathon | 3:20:41 | 4:45 | 7:39 |
Training paces for this fitness
| Run | Per km | Per mile | What it is for |
|---|---|---|---|
| Easy | 5:08 to 5:55 | 8:16 to 9:31 | Most of your running: conversational, builds the base. |
| Marathon | 4:45 | 7:39 | Steady, controlled race-effort running. |
| Threshold | 4:28 | 7:11 | Comfortably hard: tempo runs and cruise intervals. |
| Interval | 4:07 | 6:37 | Hard repeats of 3 to 5 minutes with jog recoveries. |
| Repetition | 3:52 | 6:14 | Short, fast repeats with full recovery, for speed and form. |
How to use these numbers
- Run most of your weekly distance at the easy pace. If you can only speak in short sentences, slow down.
- Keep threshold and interval work to a small share of the week, and add it gradually.
- Hot, hilly or windy? Judge hard sessions by effort, not pace.
- Re-check your numbers after a new race or a hard time trial: fitness changes, and so should your paces.
Turn this into a plan
Runergy Lab builds a week-by-week plan from your own race time, with these paces, the long runs and the easy weeks, and re-plans when life gets in the way. See the faster-5K plan or build your own.
Questions
Is a 21:00 5K a good time?
It depends on your age, experience and goals. A 21:00 5K is an average pace of 4:12 per kilometre (6:46 per mile), which is equal in effort to 10K in 43:32. Use it as a starting point for training, not a verdict.
What should my easy pace be if I run a 21:00 5K?
About 5:08 to 5:55 per kilometre (8:16 to 9:31 per mile). Easy runs should feel conversational; threshold work sits near 4:28 per kilometre.
Faster: 20:00 5K · Slower: 22:00 5K · All race times
These are estimates, not guarantees of a future result. Pace figures round to the second.