Running Pace Calculator
Calculate running pace per km or mile from distance and time, finish time from pace, or distance covered — with split times for 5K, 10K, half and full marathon.
How pace, time and distance relate
The three quantities are locked together — know any two and the third follows:
Pace = time ÷ distance · Time = pace × distance · Distance = time ÷ pace
This calculator works in whichever direction you need: find your pace from a run you have done, predict a finish
time from a target pace, or see how far you covered in a given time. Results always show pace both per kilometre
and per mile, plus the equivalent speed, so you can compare against treadmill settings or GPS-watch readouts.
Worked example
You run 5 km in 25:00. Pace = 1,500 seconds ÷ 5 km = 300 s/km = 5:00 min/km
(about 8:03 min/mile, or 12 km/h / 7.46 mph). Held perfectly even, that pace projects a 50:00 10K, a 1:45:29
half marathon and a 3:30:59 marathon.
Using the race projections wisely
The splits table assumes a perfectly even pace, which is a best case: most runners slow as the distance grows.
A common rule of thumb is that your pace drops a few percent each time the race distance doubles — so a 5K pace
projection for the marathon is optimistic by 15 minutes or more. For race planning, base the pace on a recent
result at a similar distance, and start a touch slower than goal pace rather than faster: seconds banked early
are usually repaid with interest late in the race.
Common target paces
- 30-minute 5K: 6:00 min/km (9:39 min/mile)
- 60-minute 10K: 6:00 min/km (9:39 min/mile)
- 2-hour half marathon: 5:41 min/km (9:09 min/mile)
- 4-hour marathon: 5:41 min/km (9:09 min/mile)
Frequently asked questions
What pace do I need for a 4-hour marathon?
A marathon is 42.195 km (26.22 mi). Four hours is 14,400 seconds, so you need 14,400 ÷ 42.195 ≈ 5:41 per km, which is about 9:09 per mile — roughly 10.5 km/h (6.6 mph) held for the full distance.
What is the difference between pace and speed?
Pace is time per distance (minutes per km or mile) and is what runners usually track; speed is distance per time (km/h or mph). They are reciprocals: 5:00 min/km equals 12 km/h, and a faster pace means a smaller number.
What is a good pace for a beginner runner?
Most beginners run easy efforts somewhere around 6:30–8:00 min/km (10:30–13:00 min/mile). The right pace is one where you could hold a conversation — speed comes later with consistent training, so comparing yourself to others is rarely useful.
How accurate are the race split projections?
They assume you hold exactly the same pace for every kilometre. Real races slow at longer distances — nobody holds their 5K pace for a marathon — so treat the longer projections as a best case, or use a recent race at a similar distance for realistic pacing.
How long is a half marathon?
A half marathon is 21.0975 km, or about 13.11 miles — exactly half the marathon distance of 42.195 km. At 6:00 min/km it takes about 2 hours 7 minutes.