How pace is calculated
Pace is simply time divided by distance:
Pace = total time ÷ distance
e.g. 25:00 ÷ 5 km = 5:00 per km
e.g. 25:00 ÷ 5 km = 5:00 per km
We convert that into pace per mile, and your average speed in both km/h and mph, so you can compare against treadmills, watches, and race targets in any units.
How race predictions work
The predicted finish times use Pete Riegel's endurance formula, the standard used across running calculators:
T2 = T1 × (D2 ÷ D1)^1.06
It projects a time at a new distance from a known result, with the 1.06 exponent accounting for the natural slow-down as distance grows. It's most accurate when you've trained appropriately for the target distance — a fast 5K won't predict a marathon you haven't built the endurance for.
Predictions assume similar terrain, weather, and that you've done the mileage. Treat them as ambitious-but-realistic targets, not guarantees.
Turning a pace goal into a finish
- Train at varied paces — easy runs build the engine, faster sessions sharpen it.
- Most of your running should feel easy — the classic mistake is running mediums every day.
- Consistency beats heroics — four steady weeks beat one huge week and three skipped ones.