How the running pace calculator works
Pace is the time it takes you to cover one kilometre or one mile. Runners use it instead of speed because it's easier to check on a watch mid-run: if you know you need to hold 5:41 per km for a sub-four-hour marathon, you can see straight away whether you're on track. The calculator uses two simple formulas:
pace = total time ÷ distance
finish time = pace × distance
A mile is exactly 1.609344km, so pace per mile is pace per km × 1.609344. Speed in km/h is 60 ÷ pace in minutes per km. The race distances are the official ones: a half marathon is 21.0975km (13.1 miles) and a marathon is 42.195km (26.2 miles). Results are rounded to the nearest second.
Worked examples
- A 30-minute parkrun: 30 minutes ÷ 5km = 6:00 per km, which is 9:39 per mile or 10km/h.
- A four-hour marathon: 4 hours is 14,400 seconds. 14,400 ÷ 42.195 = 341.3 seconds, or 5:41 per km (9:09 per mile).
- A 10k at 5:30 per km: 5.5 minutes × 10 = 55:00.
- A half marathon at 5:00 per km: 300 seconds × 21.0975 = 6,329 seconds, or 1:45:29.
Pace chart for popular race times
| Target | Pace per km | Pace per mile |
|---|---|---|
| 5k in 25:00 | 5:00 | 8:03 |
| 5k in 30:00 | 6:00 | 9:39 |
| 10k in 50:00 | 5:00 | 8:03 |
| 10k in 60:00 | 6:00 | 9:39 |
| Half marathon in 1:45:00 | 4:59 | 8:01 |
| Half marathon in 2:00:00 | 5:41 | 9:09 |
| Marathon in 3:30:00 | 4:59 | 8:01 |
| Marathon in 4:00:00 | 5:41 | 9:09 |
| Marathon in 4:30:00 | 6:24 | 10:18 |
Notice that a two-hour half and a four-hour marathon need the same pace. Holding it for twice as long is what makes the marathon so much harder, so most runners find their marathon pace is noticeably slower than their half marathon pace.
Using the split table
The split table shows where you should be at each kilometre or mile if you run at an even pace. Many runners write a few key splits on their hand or a pace band, for example the 10k, halfway and 30k marks in a marathon. Running even splits, or slightly faster in the second half (a negative split), is usually the most efficient way to race. Going off too fast in the first few miles is the most common reason people miss their target.
The "same pace over other distances" table simply multiplies your pace by each distance. It's not a race prediction: you won't be able to hold your 5k pace for a marathon. Use it to see what a pace means, for example that 6:00 per km is a 30-minute 5k or a 4:13:10 marathon.
Tips for pacing
- Most of your runs should be easy. An easy pace is one where you can hold a conversation. It's usually well over a minute per km slower than your 5k race pace.
- GPS watches drift. Tall buildings, trees and tunnels can throw out the reading, and races are measured on the shortest line, so your watch will often show a little more than the official distance.
- Allow for hills and heat. Hold your effort, not your pace, on hills and on warm days.
- Build up gradually. If you're new to running, the free NHS Couch to 5K plan takes you from walking to running 5k in nine weeks.
Running burns a lot of energy, so the calorie calculator can help you see how much you need on training days, and the water intake calculator shows how much extra to drink when you exercise. Good sleep matters for recovery too: the sleep calculator works out when to go to bed. If you have a heart condition, chest pain or dizziness when you exercise, or you're starting running after a long break with a health condition, speak to your GP first.
Frequently asked questions
What pace do I need for a sub-30 minute 5k?
You need to average just under 6:00 per km, or 9:39 per mile. Running exactly 6:00 per km gives a 30:00 finish, so aim for about 5:55 per km to have a few seconds to spare.
What pace is a four-hour marathon?
A four-hour marathon is 5:41 per km or 9:09 per mile. That's 14,400 seconds spread over 42.195km.
How do I convert pace per km to pace per mile?
Multiply your pace per km by 1.609344. For example, 5:00 per km is 300 seconds × 1.609344 = 483 seconds, or 8:03 per mile.
What is a good 10k time for a beginner?
Many beginners finish a 10k in 60 to 75 minutes, which is a pace of 6:00 to 7:30 per km. Anything you can run comfortably and improve on is a good time.
How far is a half marathon in km and miles?
A half marathon is 21.0975km, or 13.1 miles. A full marathon is 42.195km, or 26.2 miles.
Last reviewed October 2026 using 2026/27 figures. This calculator gives an estimate for guidance only.