Pace Calculator

A pace calculator divides your time by your distance. A 10K is 6.2137 miles, so running it in 50:00 means 3,000 seconds ÷ 6.2137 ≈ 483 seconds per mile, a pace of 8:03 per mile or 5:00 per kilometer. Turn the formula around to get a finish time (pace × distance) or a distance (time ÷ pace).

How to use the pace calculator

1. Choose what you want to find: pace, finish time or distance. Use the Treadmill tab to turn a speed in mph or km/h into a pace.
2. Pick pace per mile or per kilometer at the top.
3. Pick a race (5K, 10K, half marathon, marathon and more) to fill in its exact distance, or type any distance in miles, kilometers or meters.
4. Enter the time in hours, minutes and seconds, or the pace in minutes and seconds.
5. Read the answer, then check the even-pace split table and the race time predictor. Open Show steps to see the working.

When you switch tabs, the value you just solved moves into the new form. Find your pace for a 10K, click Finish time, pick a half marathon, and you see how long that pace would take over 13.1 miles.

Pace formula: pace, time and distance

Pace, time and distance are linked by one relationship, the same one behind speed. If you know any two, you can find the third:

• Pace = time ÷ distance
• Time = pace × distance
• Distance = time ÷ pace

Here time is the total time of the run, distance is in miles or kilometers, and pace is the time for one mile or one kilometer. The easiest way to do it by hand is to change everything to seconds first, do the division or multiplication, then change seconds back to minutes and seconds by dividing by 60.

Pace and speed are reciprocals. Speed tells you how far you go in an hour. Pace tells you how long one unit of distance takes:

• Pace in seconds per mile = 3,600 ÷ speed in mph
• Pace in seconds per kilometer = 3,600 ÷ speed in km/h

To switch between miles and kilometers, use the exact definition: 1 mile = 1,609.344 meters, so 1 mile = 1.609344 km and 1 km ≈ 0.621371 miles. A pace per kilometer is always shorter than the matching pace per mile, because a kilometer is the shorter distance.

Pace calculation examples

Example 1: marathon pace for a 3:30 finish

A marathon is 42.195 km, which is 42,195 ÷ 1,609.344 ≈ 26.2188 miles. The goal time is 3 h 30 min = 12,600 seconds. Pace = 12,600 ÷ 26.2188 ≈ 480.6 seconds per mile. Since 480 seconds is 8 minutes, the pace is about 8:01 per mile. Per kilometer it is 12,600 ÷ 42.195 ≈ 298.6 seconds, or 4:59 per km.

Example 2: half marathon finish time at 9:00 per mile

A half marathon is 21.0975 km, or about 13.1094 miles. A 9:00 pace is 540 seconds per mile. Time = 540 × 13.1094 ≈ 7,079 seconds. Divide by 3,600 to get 1 hour with 3,479 seconds left, and 3,479 seconds is 57 minutes 59 seconds. The finish time is 1:57:59.

Example 3: treadmill speed of 6.5 mph

Pace = 3,600 ÷ 6.5 ≈ 553.8 seconds per mile, which is 9 minutes and about 14 seconds, so 9:14 per mile. In metric, 6.5 mph × 1.609344 ≈ 10.46 km/h, and 3,600 ÷ 10.46 ≈ 344 seconds, or 5:44 per km.

Race distances in miles and kilometers

The calculator uses the official distances. World Athletics gives the marathon as 26 miles 385 yards (42.195 km) and the half marathon as exactly half of that, 21.0975 km.

Pace chart for common goal times

Paces are rounded to the nearest second. A 2-hour half marathon and a 4-hour marathon need the same pace, because the marathon is exactly twice as long.

Even-pace splits

A split is the time for one segment of a race, usually each mile or kilometer. The split table assumes even pacing: every mile (or km) takes the same time, and the last row covers the leftover part of the distance. The elapsed column is the time you should see on your watch at each marker. For a 10K in 50:00 at 8:03 per mile, mile 3 should pass at about 24:08 and the last 0.21 miles takes about 1:43.

Race time predictor: Riegel’s formula

To estimate a time at a new distance from a recent race, the calculator uses the formula published by Peter Riegel in American Scientist in 1981:

T2 = T1 × (D2 ÷ D1)^b

T1 and D1 are your known time and distance, D2 is the new distance and b is the fatigue exponent. Most calculators use b = 1.06. In the paper, Riegel’s fitted value for world-class runners is about 1.08 (1.077 for men and 1.083 for women), and he reports 1.05 to 1.06 for men aged 40 to 70. You can pick any of these values in the tool. A 10K in 50:00 with b = 1.06 predicts 3,000 × (42.195 ÷ 10)^1.06 ≈ 13,801 seconds, or about 3:50:01 for a marathon.

Riegel fitted his formula to performances lasting about 3.5 to 230 minutes, so the tool marks predictions outside that range. The result is only an estimate. It assumes you train for the new distance and race on a similar course, and the further apart the two distances are, the less reliable it gets.

Common pace mistakes

• Treating decimal minutes as seconds. 8.5 minutes is 8:30, not 8:50. Multiply the decimal part by 60.
• Using 26.2 miles for a marathon. The real distance is about 26.2188 miles. At 8:00 per mile the difference is about 9 seconds.
• Mixing units. A time divided by kilometers gives pace per kilometer, not per mile.
• Averaging paces from different distances. Find total time ÷ total distance instead. A plain average of paces gives the wrong answer when the segments are different lengths.

Sources

Checked November 2026.

• World Athletics: Marathon (26 miles 385 yards, 42.195 km)
• World Athletics: Half marathon (21.0975 km, 13.1094 miles)
• Riegel PS. Athletic Records and Human Endurance. American Scientist. 1981;69(3):285-290 (PDF copy)
• NIST: U.S. Survey Foot, Revised Unit Conversion Factors (1 mile = 1,609.344 m)

Running pace practice quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

How do I calculate my running pace?

Divide your total time by your distance. Change the time to seconds first. For example, 30:00 for 3.1069 miles (a 5K) is 1,800 ÷ 3.1069 ≈ 579 seconds, which is 9:39 per mile.

How do I convert mph to minutes per mile?

Divide 60 by the speed. At 6 mph, 60 ÷ 6 = 10 minutes per mile. At 7.5 mph, 60 ÷ 7.5 = 8 minutes per mile. For km/h, 60 ÷ speed gives minutes per kilometer.

What pace do I need for a 4-hour marathon?

About 9:09 per mile or 5:41 per kilometer. That is 14,400 seconds ÷ 26.2188 miles ≈ 549 seconds per mile.

How accurate is a race time predictor?

Treat it as a rough estimate. It works best when the two races are not too far apart in distance and you have trained for both. Riegel fitted his formula to efforts of about 3.5 to 230 minutes, so a prediction from a mile to a marathon is much less certain than one from a 10K to a half marathon.

How many miles is a half marathon?

A half marathon is 21.0975 km, which is about 13.1094 miles. It is usually written as 13.1 miles.

Related calculators

• Time calculator to add or subtract hours, minutes and seconds
• Unit converter for miles, kilometers and other lengths
• Unit rate calculator for any "per one" rate
• Percent change calculator to measure how much your pace improved