Half Marathon Pace Calculator: Find Your Race Pace

A half marathon pace calculator estimates your average pace from a finish time and race distance. Enter your planned or actual time and distance in kilometres to get pace per kilometre and average speed; the standard half-marathon distance is 21.0975 km (13.1 miles).

Formula

Average pace = finish time ÷ distance. In symbols, p = t ÷ d, where p is pace in minutes per kilometre, t is total elapsed time in minutes, and d is distance in kilometres. The second result uses v = d ÷ (t ÷ 60), where v is average speed in kilometres per hour. The factor 60 converts minutes to hours.

Enter the complete elapsed time as minutes. For example, 1 hour 45 minutes is 105 minutes, not 1.45. The defaults are 120 minutes and 21.0975 km. The calculator reports pace to two decimal places; this is a rounded display, not a more precise prediction of how evenly you will run.

Worked Example

Using the calculator’s defaults—120 minutes over 21.0975 km:

1. Divide time by distance: 120 ÷ 21.0975 = 5.6878 minutes per kilometre.
2. Round to two decimal places: the average pace is 5.69 min/km.
3. Convert 120 minutes to hours: 120 ÷ 60 = 2 hours.
4. Divide distance by elapsed hours: 21.0975 ÷ 2 = 10.55 km/h to two decimal places.

The pace shown as a decimal is not a minutes-and-seconds clock reading. The fractional part, 0.69 minute, is 0.69 × 60 = 41.4 seconds, so the displayed pace is about 5 minutes 41 seconds per kilometre. That conversion is useful when setting a watch or comparing with a pace chart.

How to Use Half Marathon Pace

Use the calculator for a target finish time, a completed race, or another distance you want to compare. To estimate the average pace needed for a target, put the target time in minutes and the intended distance in kilometres. To review a completed run, use elapsed time and the distance actually covered.

• Set a goal: Convert a finish-time target into a simple average pace reference for training or race planning.
• Review a result: Compare the average pace from a race or timed effort with your target.
• Compare distances: Enter another distance to calculate its average pace, but do not assume that pace will transfer directly to a half marathon.

Average pace describes the whole effort: total elapsed time divided by total distance. It does not say that every kilometre was run at that pace. Stops, hills, turns, weather, and changes in effort can make individual split times differ substantially.

Understanding the Half-Marathon Distance

A half marathon is half the standard marathon distance: 13.1 miles, conventionally expressed more precisely as 21.0975 kilometres. Race courses may be measured or displayed in miles or kilometres, and a GPS watch’s recorded distance may differ slightly from the course measurement. For a meaningful calculation, use the same distance basis throughout and distinguish the official course distance from a device’s estimate.

If you prefer minutes per mile, convert the pace rather than entering a mile distance in the kilometre calculator. Multiply minutes per kilometre by 1.609344 to obtain minutes per mile. For example, 5.69 min/km × 1.609344 is about 9.16 min/mile; the decimal fraction is approximately 9 minutes 10 seconds per mile. Alternatively, calculate directly using distance in miles and express the result in minutes per mile. Do not divide minutes by kilometres and label the answer min/mile.

Common Input and Rounding Mistakes

• Entering hours as a decimal: A time of 1:45 is 105 minutes. Entering 1.45 minutes or 1.75 hours in a minutes field gives the wrong result.
• Mixing units: The calculator’s distance field is in kilometres. If you enter 13.1 as though it were kilometres, the calculated pace will be incorrect for a half marathon.
• Confusing pace and speed: Pace is time per distance (min/km); speed is distance per time (km/h). A lower pace number means faster running, while a higher speed number means faster running.
• Rounding too early: Keep the full input distance and time for the calculation, then round the displayed pace. Converting a rounded decimal pace to seconds can produce a small difference.
• Ignoring elapsed time: Moving time excludes pauses in some timing systems, while elapsed time includes them. Choose the time that matches the question you want answered.

What the Calculator Can and Cannot Tell You

The formula is arithmetic, not a race-time prediction model. It answers what average pace corresponds to the time and distance entered. It cannot determine whether that pace is realistic for a runner, predict performance from a shorter race, or account for course elevation, temperature, fatigue, aid stops, or pacing strategy. Those factors affect an actual finish and the distribution of pace across the course, but they are not inputs to this calculation.

For instance, two runners can both average 5:41 per kilometre and finish in roughly the same time while having very different splits: one may run consistently, and another may start much faster and slow later. A pace calculator gives the common average, not a recommended race plan. Treat a target as a planning reference, and use relevant training and conditions when deciding how to pace an event.

Frequently Asked Questions

What pace do I need to finish a half marathon in two hours?
For 21.0975 km in 120 minutes, the average is about 5.69 min/km, or approximately 5 minutes 41 seconds per kilometre. That is about 9 minutes 10 seconds per mile.

How do I calculate half marathon pace by hand?
Convert the finish time to minutes, then divide by 21.0975 for minutes per kilometre. For minutes per mile, divide by 13.1 instead. Convert any decimal fraction of a minute to seconds by multiplying it by 60.

Is 5:30 per kilometre fast enough for a half marathon under two hours?
At a steady 5 minutes 30 seconds per kilometre, 21.0975 km takes about 116 minutes, or roughly 1 hour 56 minutes. Actual elapsed time can vary with pacing, course conditions, and stops.

What is the difference between pace and speed?
Pace is the time needed to cover a unit of distance, such as minutes per kilometre. Speed is distance covered per unit of time, such as kilometres per hour; they describe the same average effort in inverse forms.

Why does my GPS watch show a different pace from the calculator?
The calculator uses the time and distance you enter. A watch may use a slightly different recorded distance, moving time, or averaging method, so its displayed pace can differ. Check that both figures use the same distance and elapsed-time basis.

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in t | Finish time | min | 120 | 0
in d | Distance | km | 21.0975 | 0
out pace | Average pace | min/km | t / d | 2
out speed | Average speed | km/h | d / (t / 60) | 2