The conversion, and the three constants it rests on
Everything here is one number wearing different clothes. Speed is distance over time; pace is time over distance; they are reciprocals, and the only thing that changes between the five outputs is which units the numerator and denominator are in.
Three definitions do all the work and none of them are approximations. The international mile is exactly 1,609.344 metres, fixed by the 1959 international yard and pound agreement — which also fixes the yard at exactly 0.9144 m and the foot at exactly 0.3048 m. An hour is exactly 3,600 seconds. A kilometre is exactly 1,000 metres. So converting minutes per mile to minutes per kilometre is a division by 1.609344 with no rounding error introduced anywhere, and any disagreement between two calculators is one of them truncating, not one of them being wrong.
| Per mile | Per km | mph | km/h | m/s |
|---|---|---|---|---|
| 5:00 | 3:07 | 12.00 | 19.31 | 5.364 |
| 6:00 | 3:44 | 10.00 | 16.09 | 4.470 |
| 7:00 | 4:21 | 8.57 | 13.79 | 3.832 |
| 8:00 | 4:58 | 7.50 | 12.07 | 3.352 |
| 9:00 | 5:36 | 6.67 | 10.73 | 2.980 |
| 10:00 | 6:13 | 6.00 | 9.66 | 2.682 |
| 12:00 | 7:27 | 5.00 | 8.05 | 2.235 |
| 15:00 | 9:19 | 4.00 | 6.44 | 1.788 |
Why every sport picked a different unit
The choice is not arbitrary. Runners use pace because a race is a fixed distance and the useful question is how long it will take — pace multiplies straight into finish time and speed does not, without a division. Cyclists use speed because the limiting factor is aerodynamic drag, which scales with the cube of velocity for power, and because a ride is usually a fixed duration or a fixed route where instantaneous speed is what varies. Swimmers use time per hundred because the pool is quantised into lengths. Rowers use time per 500 m for the same reason ergometers do. Physicists use metres per second because it is the SI unit and everything else is a compound of it.
The unit you count in shapes what you notice. Speed makes small differences at the fast end look small — 10.0 to 10.5 mph is five percent — while pace makes the same change look like the 17 seconds per mile it is. Neither view is wrong, but pacing a race off a speed readout is harder than it needs to be.
The 400 m lap and the imperial ghost
A modern outdoor track is 400 metres in lane one, measured 30 cm out from the inside kerb. Older US tracks were 440 yards, which is 402.336 m — one mile was exactly four laps, and this is why the "quarter mile" survives as a phrase long after the tracks stopped being that length. On a 400 m track, four laps is 1,600 m, which is 9.344 m short of a mile: the difference is about 1.4 seconds at a 4:00 mile pace, which is why the metric mile and the mile are recorded as separate events rather than treated as equal.
The split table above gives both. Lane one is the only lane where the distance is what the track says; each lane outward adds roughly 7 to 8 m per lap depending on the track's kerb radius, so running a workout in lane four adds around a hundred metres per mile and quietly makes your splits look worse than they are.
Where the conversion stops being enough
A converted speed is exact and a converted effort is not. The same 8:00 per mile is a different physiological event on a flat road, on a 6 percent grade, at 7,000 feet of altitude, into a headwind, and on the eighteenth mile of a marathon. Grade in particular is large: the metabolic cost of running uphill rises steeply with slope and the saving coming back down does not compensate, which is why hilly courses run slower than flat ones even when net elevation change is zero.
Treat this page as unit arithmetic, which it does perfectly, and treat any statement about what a speed will feel like as a separate question with a different answer on every course.
Questions people ask
What is 8:00 per mile in km/h?
12.07 km/h. The chain is 8 minutes per mile, so 60 divided by 8 gives 7.5 mph, and 7.5 times 1.609344 gives 12.0701 km/h. In pace terms it is 4:58.3 per kilometre. The clean landmarks nearby are 8:03 per mile, which is exactly 12.00 km/h, and 5:00 per kilometre, which is exactly 12.00 km/h as well — the second one is exact by construction because 60 divided by 5 is 12.
Why does my GPS watch show a different average speed than distance divided by time?
Because most watches report moving average by default, excluding time when they judged you to be stopped, while distance over elapsed time includes it. On a run with traffic lights those two can differ by several percent. There is also a rounding question: watches typically display pace to the second and distance to two decimals, and recomputing from the displayed values will not exactly reproduce the displayed pace. Neither is a bug; check which average your device is reporting before concluding anything.
What is a knot in these units?
One knot is one nautical mile per hour, and a nautical mile is exactly 1,852 metres, so a knot is 1.852 km/h, 1.1508 mph, or 0.5144 m/s. It exists because a nautical mile is one minute of latitude, which makes chart navigation arithmetic trivial and has nothing to do with running. This page does not offer it as an input for that reason.
Can I use this for cycling or swimming?
The unit conversion applies to any speed. The split checkpoints are running-shaped — a 400 m lap and a quarter mile are not natural cycling units — and the treadmill chart is obviously running-only. For cycling the useful frame is usually speed rather than pace, and for swimming the useful frame is time per 100 yards or metres, which this page does not present. The arithmetic is correct for all of them; the framing is built for running.