Pace Calculator: Running Pace per Mile and Km

How the pace calculator works

Pace is time divided by distance. The calculator turns your hours, minutes, and seconds into total minutes, converts the distance to kilometers (1 mile = 1.609344 km, the exact international definition), and divides. Pace per mile is then pace per km multiplied by 1.609344.

Speed is the inverse: 60 divided by pace in minutes gives miles per hour or kilometers per hour. The finish-time tiles multiply your pace by the official race distances: 5 km, 10 km, 21.0975 km for a half marathon, and 42.195 km for a marathon.

Seconds are rounded once, at the end. Plenty of pace charts round the decimal minute first and end up printing nonsense like 8:60. This one will not.

Worked example: a 28-minute 5K

A 5K is 5 km, or 3.10686 miles. Finish in 28:00 and your pace is 28 ÷ 3.10686 = 9.012 minutes per mile. The 0.012 is a fraction of a minute, so multiply by 60 to get 0.7 seconds. Pace: 9:01 per mile, or 5:36 per km (28 ÷ 5 = 5.6 minutes, and 0.6 × 60 = 36 seconds).

Speed is 60 ÷ 9.012 = 6.66 mph. Hold that exact pace for a 10K and you finish in about 56:00. Hold it for a marathon and the math says 3:56:18, but that is a best case, not a prediction.

Why your 5K pace will not carry to a marathon

Every runner slows as distance goes up. The most widely used adjustment is Pete Riegel's formula, published in 1977: T2 = T1 × (D2 ÷ D1)^1.06. Plug in a 28:00 5K and it predicts about 58:23 for a 10K, 2:08:48 for a half marathon, and 4:28:33 for a marathon.

So the even-pace projections on this page are ceilings. Use them to check whether a goal is realistic. If your 5K pace times 42.195 barely reaches your marathon goal, the goal is too aggressive. Riegel's formula also assumes you trained for the distance; it gets less reliable past about 3 hours of running if your long runs are short.

Using pace for training, not just racing

Most of your weekly miles should feel easy. A common rule of thumb puts easy pace at roughly 60 to 90 seconds per mile slower than your 5K race pace, so the 9:01 runner above would do easy runs around 10:00 to 10:30 per mile. If you can hold a conversation, you are in the right zone.

Tempo runs sit near the pace you could hold for one hour, which for many recreational runners lands between 10K and half marathon pace. Intervals go at 5K pace or faster. The calculator is handy for turning a treadmill setting into a pace: 6.0 mph is exactly 10:00 per mile, 7.5 mph is 8:00 per mile.

Common pace mistakes

Typing 9.30 when you mean 9:30. Nine and a half minutes is 9.5 decimal minutes, not 9.30. Always enter minutes and seconds separately, which is why this calculator has three time fields.

Trusting GPS distance blindly. Watches often read 1 to 3 percent long or short, especially under trees, between tall buildings, and on tight tracks. Races are measured along the shortest possible line, so your watch will almost always show more than 26.2 miles for a marathon. That extra distance is why chip time pace and watch pace disagree.

Starting too fast. Going out 20 seconds per mile faster than goal pace in the first mile feels great and costs more than 20 seconds later. Even or slightly negative splits are how most personal bests happen.

US race context

American races mark miles, while most of the world marks kilometers, and many US marathons show both. Boston Marathon qualifying times are set by age and gender; for 2026 the men's 18 to 34 standard is 2:55 (6:40 per mile) and the women's is 3:25 (7:49 per mile). Check the Boston Athletic Association site for your exact group, because the cutoff time needed to get in has been faster than the standard in recent years.

For track workouts, one lap of a standard outdoor track is 400 meters, about 0.2485 miles. Four laps is 1,600 meters, 9.34 meters short of a full mile, so a 1,600 m split is a touch faster than true mile pace.