How the running pace calculator works
Pace, time and distance are three sides of one simple relationship. If you know any two of them, the third is fixed. That is all this calculator does — it rearranges a single equation so you can plan a goal race, check a training run, or convert your effort between kilometres and miles without reaching for a spreadsheet.
The formula
Everything follows from the definition of pace as time over distance:
- Pace =
time ÷ distance - Time =
pace × distance - Distance =
time ÷ pace
Internally the tool converts every distance to kilometres (using
1 mile = 1.609344 km and 1 km = 1000 m) and every time to seconds, so
the arithmetic is always consistent. Speed is the inverse view of pace:
speed = distance ÷ time, reported in both km/h and mph.
A worked example
Suppose you run 10 km in 50 minutes. Time in seconds is
50 × 60 = 3000 s. Your pace is 3000 ÷ 10 = 300 s/km, which is
5:00 per kilometre. To express that per mile, multiply by 1.609344:
300 × 1.609344 ≈ 483 s, or about 8:03 per mile. Your speed is
10 ÷ (3000 ÷ 3600) = 12 km/h — roughly 7.46 mph.
Common race paces
| Goal | Distance | Pace /km | Pace /mile |
|---|---|---|---|
| Sub-25 5K | 5 km | 5:00 | 8:03 |
| Sub-50 10K | 10 km | 5:00 | 8:03 |
| Sub-2:00 half | 21.0975 km | 5:41 | 9:09 |
| Sub-4:00 marathon | 42.195 km | 5:41 | 9:09 |
| Sub-3:30 marathon | 42.195 km | 4:59 | 8:01 |
Three modes
Solve for pace, finish time or distance — the calculator hides the field you are solving for and asks only for the two you know.
km or miles
Mix and match units freely. Enter distance in miles, set pace per kilometre, and the conversion is handled for you.
Race presets
One tap fills in 5K, 10K, half marathon (21.0975 km) or marathon (42.195 km) at their official distances.