Running Pace Calculator Widget

Add a running pace calculator to your website. Runners pick a race distance or enter their own, then either type a finish time to see pace and speed or type a target pace to see the finish time, with equivalents for 5K, 10K, half marathon and marathon.

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<iframe src="https://a2z.tools/embed/w/running-pace-calculator" title="Running Pace Calculator by A2Z Tools" width="100%" height="790" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.

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How it works

It is the same arithmetic as the A2Z Running Pace Calculator, extended to work in both directions. Race presets use the standard road distances (half marathon 21.0975 km, marathon 42.195 km) and the international mile of exactly 1.609344 km, the value NIST lists. In imperial mode, custom distances and pace are entered per mile. Times are kept in full precision and rounded to whole seconds only when shown, so a 4:15.96 pace displays as 4:16 rather than drifting through the conversions. The equivalents table shows what the same even pace gives over the standard race distances; the widget notes that real race times over longer distances are usually slower, and it flags an average speed above 25 km/h as a probable typing mistake.

Calculation method

  • Pace = time / distance (per km and per mile); finish time = pace x distance
  • Speed = distance / time, shown in km/h and mph to 2 decimal places
  • 1 mile = 1.609344 km exactly; half marathon = 21.0975 km; marathon = 42.195 km
  • Times rounded to the nearest whole second only for display (59.6 s shows as 1:00)

Worked examples

Sub-3 marathon target

Inputs: Marathon, 3:00:00

Result: 4:16 /km, 6:52 /mi, 14.07 km/h; same pace gives 5K 21:20, 10K 42:40, half 1:30:00

10,800 s / 42.195 km = 255.96 s per km.

Limitations

  • Assumes an even pace on a measured course; hills, wind, heat and GPS distance errors are ignored.
  • The equivalents are not race-time predictions such as Riegel's formula, which allow for fatigue over longer distances.

Where publishers use it

  • Running clubs and parkrun-style community sites
  • Race-organiser pages, so entrants can plan pacing for the course distance
  • Coaching blogs publishing training plans with target paces
  • Sports-shop and running-shoe sites with a training resources section

Questions

Can it convert pace per km to pace per mile?

Yes. Every result shows both, and the Metric/Imperial switch decides which one is entered and highlighted.

Are the race equivalents predictions?

They are even-pace equivalents, not race predictions. Most runners slow over longer distances, so a 10K pace held for a marathon is usually optimistic.

What pace is a 3-hour marathon?

10,800 seconds over 42.195 km is 4:16 per km or 6:52 per mile, about 14.07 km/h.

Can I set a default distance?

Yes. Use v_distance=half (or 5k, 10k, marathon, mile, custom) and v_mode=time for the pace-to-finish-time mode.

Sources

  1. NIST Guide to the SI, Appendix B.8 - conversion factors - National Institute of Standards and Technology (SP 811) . International mile = 1,609.344 m

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Running Pace Calculator
https://a2z.tools/running-pace-calculator

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