Half Marathon Pace Calculator

Enter your target finish time for the half marathon (13.11 mi / 21.0975 km) and get the exact pace you need per mile and per kilometer, plus your average speed.

Quick Facts

Method
Finish time ÷ 13.1094 mi (21.0975 km)
Pace and speed are exact for a constant even effort.

Your Results

Calculated
Pace per mile
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min:sec per mile
Pace per km
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min:sec per kilometer
Average speed
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miles per hour
Average speed
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kilometers per hour

Ready

Enter a target finish time and press Calculate.

About half marathon pace

A half marathon is exactly 21.0975 kilometers, which equals 13.1094 miles — 13 miles plus 192.5 yards, or precisely half the official marathon distance of 42.195 km. This calculator takes the finish time you want and divides it by that fixed distance to tell you the steady pace and average speed you must hold to hit it.

The formula

Pace is simply target time divided by distance, and speed is distance divided by time:

  • Pace per mile = finish time (seconds) ÷ 13.1094
  • Pace per km = finish time (seconds) ÷ 21.0975
  • Average speed (mph) = 13.1094 ÷ finish time (hours)
  • Average speed (km/h) = 21.0975 ÷ finish time (hours)

For example, a 1:45:00 target is 6,300 seconds. Dividing by 13.1094 gives 480.6 seconds per mile, or 8:01 per mile; dividing by 21.0975 gives 298.6 seconds per km, or 4:59 per km. Average speed is 13.1094 ÷ 1.75 h = 7.49 mph (12.06 km/h).

Common target paces

These are the even paces required for popular round-number finish times:

  • 1:30:00 — 6:52 /mi (4:16 /km), 8.74 mph
  • 1:45:00 — 8:01 /mi (4:59 /km), 7.49 mph
  • 2:00:00 — 9:09 /mi (5:41 /km), 6.55 mph
  • 2:15:00 — 10:18 /mi (6:24 /km), 5.83 mph
  • 2:30:00 — 11:27 /mi (7:07 /km), 5.24 mph

Why even pacing matters

The calculator gives you a single steady pace because even effort — or a slight negative split, where the second half is run marginally faster than the first — produces the best half marathon results for nearly all runners. The most common execution error is going out 15–30 seconds per mile too fast in the first two miles, which spends glycogen early and forces a painful slowdown after mile 9. Banking time rarely works; the seconds you gain early are usually lost with interest late.

Adjusting for real-world conditions

The result assumes a flat course in good conditions. Hills, heat, and altitude all cost time the arithmetic can't see. Expect to add roughly 20–30 seconds per mile for every 10°F above about 60°F, a similar penalty at altitudes above 5,000 ft until you acclimatize, and extra time on hilly or trail courses. Use the calculated pace as your flat-ground goal, then set a slightly slower "adjusted" target on tough days.

Frequently Asked Questions

How long is a half marathon?
A half marathon is exactly 21.0975 km, which is 13.1094 miles (13 miles plus 192.5 yards). It is half the official marathon distance of 42.195 km. This calculator uses that exact distance to convert your target finish time into a required pace.
What pace do I need to run a 2-hour half marathon?
To finish in 2:00:00 you must average about 9:09 per mile (5:41 per km), an average speed of 6.55 mph or 10.55 km/h. To break 2 hours, aim for 9:08 per mile or faster. Because there is no margin for a slow patch, most runners target 9:05 per mile and treat the extra seconds as a buffer.
Is the result in minutes per mile or per kilometer?
Both. The calculator shows pace per mile and pace per kilometer side by side, plus average speed in mph and km/h, so you can match whatever your GPS watch or race clock displays. All four figures describe the same effort — just in different units.
How accurate is the calculated pace?
The pace is mathematically exact for a perfectly even effort on a flat, accurately measured course. Real races vary: GPS watches often over-measure distance on turns, so you may need to run a few seconds per mile faster than the tangent line suggests. Hills, wind, heat, and altitude add time the formula does not model.

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