Pace Calculator - Running Time, Distance, and Pace

A pace calculator rearranges one identity: time = pace × distance, with pace stored as seconds per kilometre or per mile. You choose which of the three quantities is unknown. The default example solves pace from 5 km in 25:00: 1,500 seconds ÷ 5 = 300 seconds per km, displayed as 5:00 /km. Multiplying by 1.609344 km per international mile gives about 8:02.8 /mi (often rounded in conversation to 8:02 /mi). If that same pace were held even, a 10 km would be 50:00, a half marathon (21.0975 km) about 1:45:29, and a marathon (42.195 km) about 3:30:59. Those extras are constant pace arithmetic, not a claim that you can run a marathon at 5k tempo.

Time is parsed as mm:ss or h:mm:ss. 25:00 is twenty-five minutes, not twenty-five seconds. Pace uses the same clock strings so 5:00 means five minutes per unit. Distance is a positive number in the selected unit. Switching km ↔ miles converts the display of equivalent pace; it does not silently reinterpret 5 as 5 miles when you meant kilometres. Always check the unit selector.

This page is running only. Cycling uses power, aerodynamics, and grade; swimming uses stroke and current. We will not emit watts, CSS, or a bike indoor trainer target. Treadmill incline, trail vert, heat, and wind all change metabolic cost at the same clock pace. For estimated kilocalories of an activity name, use the calories burned calculator; for pulse zones, the target heart rate calculator. Neither is a substitute for this identity, and this identity is not a training prescription.

1. Choose kilometres or miles and whether to solve for pace, time, or distance.
2. Fill the other two fields. Type clock times with a colon. Pace is per selected unit (min/km or min/mi).
3. Read the solved value, the equivalent pace in the other unit, and optional even-split 10k / half / marathon times.
4. Copy if you need a record. Inputs stay in this browser up to 30 days and are never uploaded. Adjust race-day goals for hills, weather, and fitness-not just this quotient.

Internally, 25:00 is 25 × 60 = 1,500 s. Distance 5 km gives 300 s/km. Formatted without hours: 5:00. Mile pace is 300 × 1.609344 = 482.8032 s/mi = 8 minutes + 2.8032 seconds. Speed in km/h is 3600 / pace_seconds_per_km = 12 km/h, which is a common easy-to-steady running speed for many recreational athletes and a brisk effort for others-the number does not know your history.

Solving for time: 8 km at 5:00 /km is 8 × 300 = 2,400 s = 40:00. Solving for distance: 1:10:00 at 5:00 /km is 4,200 / 300 = 14 km. In miles, 3.1 mi (about a 5k) in 25:00 is 25:00 / 3.1 ≈ 8:03.9 /mi depending on how you round 5 km to 3.1. This page uses 5 exactly when you type 5 in km mode rather than substituting 3.10686 unless you enter that mile distance yourself.

Even-split projections use IAAF/World Athletics road distances: 10 km, 21.0975 km half, 42.195 km marathon. A 5:00 /km marathon is 42.195 × 300 = 12,658.5 s = 3:30:58.5, displayed with a tenth of a second when needed. Positive splits, aid stations, and “hitting the wall” are not modelled. Daniels VDOT, Riegel exponents (T2 = T1 × (D2/D1)^1.06), and critical velocity are different models and are not implemented here so the page cannot be mistaken for a physiology engine.

A 400 m track lap at 5:00 /km is 2:00 per lap because 400 m is 0.4 km. 200 m would be 1:00. Those conversions assume a standard 400 m oval measured on the running line; lane 8 is longer if you do not break in. Indoor 200 m tracks and oversized “400 m” paths need their own measured distances.

Treadmill belt pace is still min/km, but a 1% incline is often used as a crude outdoor-air equivalent in coaching folklore. This calculator does not apply a 1% rule. Downhill can make the same pace cheaper until eccentric muscle damage shows up the next day. GPS watches add distance error in cities and switchbacks; garbage-in distance yields garbage-out pace.

Kilometre and mile cultures talk past each other. 7:00 /mi is about 4:21 /km (420 s/mi ÷ 1.609344 ≈ 261 s/km). 4:00 /km is about 6:26 /mi. Memorizing a few landmarks (8:00 /mi ≈ 5:00 /km is close but not exact-8:00 /mi is 4:58.2 /km) prevents mixing a marathon plan written in miles with a watch set to km.

Indoor cycling “pace” is meaningless without a power meter or a known erg. We refuse to output watts from running pace. Swimming pace per 100 m is a different unit family. If you need energy cost, METs on the calories-burned page are still averages.

Chest pain, unexplained breathlessness, or syncope during running are medical issues. A pace table will not clear you for a race. Beginners should progress volume gradually; sudden 50-mile weeks at a newly calculated “easy pace” are how people get injured. This site’s BMI calculator and one-rep max calculator are likewise estimates, not coaching.

Even splits are a teaching device. Championship marathons are often slightly positive or negative depending on tactics and weather. Your 5k PR pace is not your marathon pace. The projections exist so you can see how brutal a “just hold 5k pace” thought experiment is at 42 km-not so you attempt it.

Search traffic wants “pace chart 10k,” “how to calculate running pace,” “5k in 25 minutes pace,” and “marathon pace calculator.” 5k in 25:00 is 5:00 /km. 10k in 50:00 is the same pace. A 3:30:00 marathon is 3,780 s / 42.195 ≈ 89.58 s per km? Wait: 3:30:00 is 12,600 s, 12,600 / 42.195 ≈ 298.61 s/km ≈ 4:58.6 /km, slightly faster than 5:00. Our default 5:00 /km marathon is 3:30:58.5 because 42.195 × 5 minutes is 210.975 minutes.

Worked extras: 1 mile in 8:00 → 8:00 /mi ≈ 4:58 /km. 21.1 km in 1:45:00 → 1:45:00 is 6,300 s, 6,300 / 21.1 ≈ 298.6 s/km ≈ 4:58.6 /km. 42.2 km in 4:00:00 → 14,400 / 42.2 ≈ 341.2 s/km ≈ 5:41 /km. 400 m in 2:00 on a track → 5:00 /km if the 400 m is true. Those examples are unit hygiene, not goals.

After the clock math, fueling and heart rate are separate jobs. Daily intake estimates live on the calorie calculator. This page only divides time by distance.

Consumer GPS often reads long on switchbacks and short under dense canopy. If your watch says 5.20 km for a certified 5 km loop, the displayed pace is optimistic. Certified road courses use the calibrated bicycle method with a short course prevention factor; your neighborhood Strava segment does not. Indoor track distance is honest if you count laps on a measured oval. Treadmill belts stretch and speedometers drift; a footpod or a measured track session still beats an uncalibrated console.

Relay legs, ultramarathons, and orienteering add navigation time that is not “pace.” This solver will happily divide a 24-hour clock by 100 km and print a number that has nothing to do with runnable quality. The 500 km input cap is only a typo guard. We will not output an aid-station plan, a gel schedule, or a caffeine protocol. Those are coaching and gut-training problems.

Heat, altitude, and illness slow you at the same intended pace. A 5:00 /km that felt easy in 10 °C can be a red-line effort at 32 °C. The page will not derate for wet-bulb temperature. Negative splits on purpose (start slower, finish faster) mean the average pace is not the opening kilometre pace-enter the splits you actually care about rather than forcing one average on a tactical race.

Unit traps continue to injure training logs: typing 3.1 in km mode when you meant 3.1 miles, or pasting 26.2 into km mode for a marathon. 26.2 km is a half-ish effort, not 42.2 km. The projections always use 10 / 21.0975 / 42.195 km internally so a miles-mode user still sees world-standard road distances. If you want a 15 km time trial projection, multiply pace by 15 yourself or solve time with distance 15.

This site’s unique storage key keeps your last distance and clock strings on the device for 30 days. That is a convenience, not a training diary with graphs. Export is the Copy button. We will not sync to Garmin or Strava. If you need heart-rate context, open the target heart rate calculator; if you need MET calories, the calories burned calculator. Keep the jobs separate so a 5:00 /km identity does not pretend to be a coach.

Parkrun 5 km, high-school 3200 m, and the rarely run 15 km all reuse the same identity. 3200 m is 3.2 km; at 5:00 /km that is 16:00. A 15 km at 5:00 /km is 1:15:00. Those are not “equivalent races” in a physiological sense; they are the same seconds-per-kilometre applied to a different distance. People search “what pace is a 25 minute 5k” and the answer on this page is 5:00 /km or about 8:02.8 /mi. People search “marathon pace for 3:30” and the even-split answer is a hair faster than 5:00 /km, as the 42.195 km factor shows. Do not confuse that with a training plan that includes easy days much slower than race pace.

Wheelchair racing, racewalking, and hiking with a pack are not this tool. Hiking “pace” on a map is often km/h including breaks. If you enter moving time only, say so in your own notes; the form cannot tell. We will not output a Naismith rule elevation adjustment. Stairs and stadium repeats make GPS distance nearly useless; use measured route length or a track.

A 4 × 400 m relay at 5:00 /km is 2:00 per 400 m if the running line is 400 m. Passing a baton adds standing time that is not pace. Indoor 200 m tracks: eight laps per 1600 m. If a coach says “put 5:00 /km on the track,” that is still 72 seconds per 300 m and 48 seconds per 200 m. Those splits assume no rail-running extra distance in lane 4. Measure the oval you actually use.

Ultra aid-station clock time is not moving time. If 100 km took 12:00:00 elapsed but 90 minutes were checkpoints, moving time is 10:30:00 and pace is 378 s/km ≈ 6:18 /km, not 7:12 /km. Enter the time definition you care about. This page cannot split moving versus elapsed. Trail ultras with 4000 m of climb make even-split marathon projections decorative. We still print 10k/half/marathon extras from the current pace so you can see how silly a 5k pace looks at 42.195 km, not so you register for a road marathon on that number.

Treadmill 1% “outdoor equivalent” is folklore, not physics for every runner. A 5:00 /km belt at 0% is easier than 5:00 /km into a headwind. Downhill 5:00 /km can still trash quadriceps. None of that appears in seconds per kilometre. Cycling “pace” remains out of scope: we will not emit watts, CdA, or indoor trainer ERG targets. Swimming per 100 m is a different unit. Keep this solver on running distance, time, and pace stored as seconds per unit.

Default grading remains 5 km in 25:00 → 5:00 /km and about 8:02.8 /mi, 10 km even split 50:00, half about 1:45:29, marathon about 3:30:58.5. Copy, clear, fullscreen, unique pace-split-track, 30-day localStorage. Not a training prescription and not cycling power.