Running Pace Calculator

What this tool is used for

• Working out the pace needed to finish a race in a target time.
• Converting a pace between minutes per kilometre and per mile.
• Predicting a finish time from a training pace.
• Working out kilometre or mile splits to carry into a target race.
• Comparing two runs on pace rather than time.

Frequently Asked Questions

What is the relationship between pace and speed?

They are reciprocals — pace is time per distance, speed is distance per time. A 5:00 min/km pace is 12 km/h. Because they invert, halving your pace doubles your speed, which is why they cannot be averaged the same way.

Why can't I average two paces directly?

For the same reason you cannot average two speeds over equal distances: it needs the harmonic mean. Running one kilometre at 4:00 and one at 6:00 gives an average of 5:00 per km only because the distances are equal — over equal TIMES the answer differs.

How do I convert min/km to min/mile?

Multiply by 1.609344, since a mile is longer. A 5:00 min/km pace is 8:03 min/mile. Note you multiply the whole decimal minutes, then convert the fraction back to seconds — treating 5:00 as 5.00 and multiplying gives the wrong seconds.

What are the standard race distances?

5K, 10K, half marathon at 21.0975 km, and marathon at 42.195 km. The marathon's odd figure comes from the 1908 London Olympics, where the course was extended to finish in front of the royal box.

What is negative splitting?

Running the second half faster than the first. Most world records are set this way, because starting conservatively preserves glycogen and delays the point where pace collapses — the opposite of most amateurs' instinct.

How much does elevation change effective pace?

Roughly 10 to 20 seconds per kilometre for every 1% of gradient uphill, with only a partial gain on the way back down. That asymmetry is why a hilly route is slower than a flat one of the same distance and total climb.

What is grade-adjusted pace?

An estimate of the flat-ground pace equivalent to the effort you actually spent on a hill. It makes runs over different terrain comparable, which raw pace cannot do — though the adjustment models are approximations, not measurements.

Common errors and gotchas

• Confusing pace with speed, which are reciprocals rather than the same quantity in different units.
• Averaging paces directly, which is wrong for a reciprocal quantity.
• Mixing per-mile and per-kilometre paces, which differ by about 60%.
• Assuming an even pace is optimal, which terrain and strategy often contradict.
• Reading a decimal pace as minutes and seconds, where 5.5 is five and a half minutes not five fifty.