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Running pace calculator

Pace per mile and per kilometre, speed in mph and km/h, time or distance of a run, race time prediction with Riegel’s formula and a split times table.

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Your run

Choose the value to calculate, then enter the other two: the result updates as you type.

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Time

Method & sources

Any two of distance, time and pace give the third: pace = time ÷ distance. Speed follows from it (60 ÷ pace in minutes). Predicted race times apply Riegel’s formula to the calculated run, and split times assume an even pace from start to finish.

Formula
Pace = time ÷ distance · Speed = 60 ÷ pace (in minutes) · Riegel: T2 = T1 × (D2 ÷ D1)^1.06

Limitations

  • Riegel fitted his formula on world records, for efforts of about 3.5 to 230 minutes; outside that range the prediction is flagged as a rough estimate.
  • For the marathon it often underestimates recreational runners’ times by 10 minutes or more, especially from a 5K or a 10K.
  • Hills, wind, heat and how well you trained for the target distance change the real finish time.
  • One mile is 1.609344 km; a half marathon is 21.0975 km (13.1 miles) and a marathon 42.195 km (26.2 miles).

Sources

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How does this tool work?

Pace is the time it takes to cover one mile or one kilometre, and it is the basic measure behind every running plan. This calculator puts three tools in one: it works out pace, time or distance from the other two, predicts your race times from 5K to marathon and lists your split times.

Choose what you are looking for: pace (from a distance and a time), time (from a distance and a pace) or distance (from a time and a pace). The 5K, 10K, half marathon and marathon buttons fill in the official distance in one click, in miles or kilometres.

The result shows at once the pace per mile and per kilometre, the speed in mph and km/h, predicted times over the classic distances with Riegel’s formula and the cumulative time at every mile or kilometre, so you can hold your goal on race day.

How to use this tool

  1. Choose the value to calculate

    Pace, time or distance; its field disappears.

  2. Enter the other two

    Use an official distance button or type your own distance, in miles or kilometres.

  3. Read your benchmarks

    Pace, speed, predicted times and splits appear as you type.

Good to know

Three calculators in one

Pace, time or distance: choose the unknown and enter the other two values.

Flagged race predictions

Riegel from 5K to marathon, with a warning when the extrapolation gets rough.

Ready-made splits

Cumulative time at every mile or kilometre, in both units.

The pace formulas

Distance, time and pace are linked: any two give the third.

Pace

pace = time ÷ distance

Time

time = pace × distance

Speed

speed = 60 ÷ pace (in minutes)

Riegel

T2 = T1 × (D2 ÷ D1)^1.06

T1, D1
Time and distance of a completed race
T2, D2
Predicted time over the target distance
1.06
Fatigue exponent: pace slows as distance grows

Predictions assume training suited to the target distance and comparable race conditions.

Use cases

Set a goal pace

Aim for a sub-25 5K or a sub-2-hour half: the tool gives the pace to hold and every split time.

Review a training run

Enter the distance and time of a run to see your average pace and speed.

Estimate a time over another distance

From a recent 10K, see your target time for a 5K or a half marathon before picking your next race.

Tips and best practices

  • Start at your planned pace rather than faster: a fast start almost always costs time in the final miles.
  • To predict a marathon, start from a recent half marathon rather than a 10K, and add a margin for a first marathon.
  • Write a few key splits on a pace band or in your watch to check your pace during the race.

Frequently asked questions

How do I calculate my running pace?

Divide your time by the distance. 6.2 miles (10K) in 50 minutes gives about 8:03 per mile; the same run is 50 ÷ 10 = 5:00 per kilometre.

How do I convert pace to speed?

Divide 60 by the pace in decimal minutes. A pace of 8:00 per mile is 60 ÷ 8 = 7.5 mph; a pace of 5:00 per kilometre is 12 km/h.

What pace do I need for a sub-2-hour half marathon?

You need to average 9:09 per mile (5:41 per kilometre), about 6.6 mph, to cover 13.1 miles in 2 hours. Choose “Pace” or “Time” in the calculator to get every matching split.

What pace is a 4-hour marathon?

A 4-hour marathon needs an average of 9:09 per mile (5:41 per kilometre) over 26.2 miles. You reach halfway in 2:00:00.

How do I predict my time over another distance?

Riegel’s formula, T2 = T1 × (D2 ÷ D1)^1.06, extrapolates a race time while allowing for slowing over longer distances. A 50-minute 10K predicts about 1:50 for the half marathon. It works well up to the half but is often too optimistic for the marathon.

Why is my marathon prediction too fast?

Riegel built his formula on world records. A 2016 study of more than 2,000 recreational runners found it underestimates marathon time by at least 10 minutes for half of them: endurance over 26.2 miles matters more than speed over a 10K.

How long exactly are a half marathon and a marathon?

A marathon is 42.195 km (26.2 miles) and a half marathon 21.0975 km (13.1 miles). Certified courses are measured with a calibrated bicycle along the shortest possible route.

What is a split time?

It is the cumulative time at a point of the course, for example at mile 5 or at 10 km. Comparing it with your goal tells you during the race whether you are ahead of or behind your pace.

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