Running Pace Calculator
Enter any race distance and finish time — get your pace per km and per mile, your speed, and predicted finish times for the other classic distances.
How the math works
predicted time = time × (new distance ÷ raced distance)^1.06 (Riegel)
Pace is just time divided by distance, expressed per kilometer or per mile. The interesting part is the Riegel formula: performance scales with distance to the power of ~1.06, so one honest race result predicts the rest. It assumes you've trained appropriately for each distance — a 5K specialist's marathon prediction will be flattering, not factual. Endurance is trained, not extrapolated.
Using your pace
Most training plans are built off your current pace, not your goal pace: easy runs about 1–1.5 min/km slower than 5K race pace, tempo runs around 10–15 s/km slower than it, intervals faster. If every run is run at the same speed, that speed is usually too fast for the easy days and too slow for the hard ones.
FAQ
- What pace do I need for a sub-2:00 half marathon?
- 5:41 per km (9:09 per mile). Enter 21.0975 km and 2:00:00 above to work backwards from any goal.
- Why is my GPS watch's pace different from this?
- Consumer GPS drifts by 1–2% typically, and races measure slightly short on tangents. Official chip times are the ground truth for pace math.
- Does terrain matter?
- Heavily. Hills and heat can cost 10–30 s/km. Compare paces on similar courses, or use grade-adjusted pace on your watch.