Running Pace Converter

What does this calculator do?

The pace converter turns one number into every other common running unit. Enter a kilometre pace, a mile pace, a 400 m split, km/h or mph, and it returns the matching min/km, min/mile, km/h, mph and 400 m time — plus the even-pace finish times those figures imply for 5K, 10K, half marathon and marathon.

Typical uses: reading a US treadmill speed (mph) as min/km, converting a track 400 m split into road pace, or checking what 5:30/km would mean as a half-marathon finish time if you held that pace all the way.

How does it work?

Every input is first turned into seconds per kilometre, which is the converter’s single internal unit. A kilometre pace is already that number; a mile pace is divided by 1.609344; a 400 m time is multiplied by 2.5 (because 1 km = 2.5 × 400 m); km/h and mph are inverted (seconds per kilometre = 3,600 ÷ km/h). From that one value the page derives every other unit, so the row of results is always internally consistent.

The finish-time table is the same arithmetic: time = pace × official race distance. It is a linear projection, not a race-prediction model — it does not add fatigue as the distance grows. For that, use the race time predictor.

Formula

s/km from min/km     = time (s)
s/km from min/mile   = time (s) ÷ 1.609344
s/km from 400 m      = time (s) × 2.5
s/km from km/h       = 3600 ÷ km/h
s/km from mph        = 3600 ÷ (mph × 1.609344)

min/mile             = s/km × 1.609344
km/h                 = 3600 ÷ s/km
mph                  = km/h ÷ 1.609344
400 m                = s/km × 0.4
finish time          = s/km × distance (km)

1.609344 is the exact international mile in kilometres. The 400 m conversion treats 400 m as exactly 0.4 km: one lap of a standard outdoor track in lane 1, with no adjustment for outer lanes or indoor 200 m tracks.

Worked example

How to interpret the result

The unit conversions are exact definitions: 5:30/km really is 8:51/mi and 10.91 km/h. Use them when a watch, a treadmill or a training plan speaks a different language from the one you think in.

The finish-time table is different. It answers “if I held this pace from start to finish, when would I finish?” A 5:30/km marathon projection of 3:52 does not mean you can run a 3:52 marathon from a 5:30 easy-run pace. For a realistic race time, start from a recent race result in the race time predictor. For treadmill incline versus outdoor pace, use the treadmill pace converter.

Assumptions and limitations

Assumptions

• The value you enter is already in the unit selected next to it.
• A 400 m split is treated as exactly 0.4 km at even pace.
• Projected finish times assume that same pace is held for the whole race distance.

Limitations

• Paces and times are rounded to the nearest second and speeds to two decimals; small differences from other converters are usually rounding.
• Finish times are linear. They ignore fatigue, hills, weather and how well you are trained for that distance.
• The 400 m figure is a road-style conversion, not a lane-adjusted track time. Lane 2–8 and indoor tracks are longer than 400.00 m on the running line.
• Treadmill belt speed is often a little high or low versus the displayed mph; this converter does not correct for calibration error or incline.
• Values faster than 1:00/km or slower than 2:00:00/km are rejected as almost certainly a unit mix-up.

Methodology and sources

Method type: Exact calculation

Unit conversions are exact arithmetic using the international mile (1.609344 km) and 400 m = 0.4 km. Projected race times are the same linear product as the pace calculator — they are not a fatigue model.

• Methodology: Pace, speed and distance
• Methodology: Speed and unit conversion
• Methodology: Rounding and displayed precision

Sources: NIST SP 811 · World Athletics Book of Rules

Last reviewed: October 9, 2026