usefulweb.site Running Pace & Splits

Everyday calculators

Running Pace & Splits

Pace, time or distance in km or miles, splits, race predictions, treadmill speed, laps.

Used when the race distance is "Custom distance".

h:mm:ss or mm:ss, e.g. 1:45:00 or 24:30.

mm:ss per km or per mile, e.g. 5:30.

%

For negative/positive splits: how much the pace changes from the start to the finish, spread evenly.

m

Try an example: 10K in 50:00: pace and splits · Marathon at 5:40/km with a 3% negative split · How far in 1 hour at 8:30/mile?

How it works

Enter two of distance, time and pace to get the third, in kilometres or miles. Get an even, negative or positive split table, race time predictions with the Riegel formula, the treadmill speed in km/h and mph, and track lap times.

  • Pace = time ÷ distance; time = pace × distance; distance = time ÷ pace. 1 mile = 1609.344 m exactly; a half marathon is 21.0975 km and a marathon 42.195 km.
  • Speed (treadmill) = 3600 ÷ pace in seconds per km (km/h) or per mile (mph).
  • Splits: for an even pace every split takes pace × split length. For a negative (positive) split the pace changes linearly along the course by the chosen percentage from start to finish, so the split times still add up to the target time.
  • Race predictions use Riegel's formula T2 = T1 × (D2 ÷ D1)^1.06, which he described for efforts of roughly 3.5 to 230 minutes. Predictions far from the input distance, and marathon times for runners without long-run training, are usually too optimistic.
  • Track laps: lap time = pace × lap length. Lane 1 of a standard track is 400 m; outer lanes are longer.

Sources

For scripts and AI agents

  • JSON API: POST https://runningpacecalculator.usefulweb.site/api/v1/calculate (same calculation as this page)
  • Interface description: OpenAPI 3.1 · AI guide: llms.txt
  • MCP server (Streamable HTTP): https://runningpacecalculator.usefulweb.site/mcp · tool name running_pace_calculator
Example request
curl -s -X POST https://runningpacecalculator.usefulweb.site/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"solveFor":"pace","preset":"10k","time":"50:00","splitUnit":"km","splitStrategy":"even"}'
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