Your running app says 6:00, your treadmill says 10, and your friend talks about miles. Are you getting faster or not? Pace and speed describe the same run in two opposite ways, and mixing them up is the most common math mistake new runners make. Here is how to read both and convert between them in seconds.
Pace measures slowness, speed measures fastness
Speed is the number most people know from driving: how many kilometres you cover in one hour (km/h). Runners, though, usually talk in pace, which flips the question around: how many minutes it takes you to cover one kilometre (or one mile). That is why pace is sometimes described as a measure of slowness rather than speed.
The practical consequence is simple but easy to forget: with pace, a smaller number means you are faster. A 5:30 per kilometre runner is quicker than a 6:00 per kilometre runner, even though 6 looks like the “bigger” result.
The two formulas you actually need
Pace is time divided by distance. Speed is distance divided by time. Because one is the flip of the other, converting between them only takes one division:
Speed (km/h) = 60 ÷ pace (minutes per km), and pace (minutes per km) = 60 ÷ speed (km/h).
The 60 is there because an hour has 60 minutes. That is all there is to it.
A real example
Say you run 5 km in 30 minutes. Your pace is 30 ÷ 5 = 6 minutes per kilometre, written 6:00/km. Your speed is 60 ÷ 6 = 10 km/h.
Now go the other way. You set the treadmill to 8 km/h. Your pace is 60 ÷ 8 = 7.5 minutes per kilometre, which is 7:30/km (not 7:50, more on that below).
Pace also tells you your finish time directly: time = pace × distance. Hold 6:00/km for a half marathon (21.0975 km) and you finish in about 2:06:35. Hold it for a full marathon (42.195 km) and you finish in about 4:13:10.
Why one minute faster is not always the same improvement
Here is the part that surprises most beginners. Because pace and speed are inverses, shaving one minute off your pace does not add the same speed every time:
- 7:00/km to 6:00/km: from about 8.6 km/h to 10 km/h (+1.4 km/h)
- 6:00/km to 5:00/km: from 10 km/h to 12 km/h (+2 km/h)
- 5:00/km to 4:00/km: from 12 km/h to 15 km/h (+3 km/h)
The faster you already are, the more extra speed each minute of pace demands. So if your first minute came quickly and the next one feels impossible, the math is part of the reason, not just your legs.
That is also why the usual advice for new runners is consistency and a slow, gradual increase in speed and distance. Sudden changes in running pace have been linked to injuries such as Achilles tendinitis, calf (gastrocnemius) injuries and plantar fasciitis.
Converting pace per km and pace per mile
Since 1959 the international mile has been fixed at exactly 1.609344 km. To convert:
- Pace per mile = pace per km × 1.609344
- Pace per km = pace per mile ÷ 1.609344
So 6:00/km becomes about 9:39 per mile, and a 10:00 per mile pace is about 6:13 per kilometre. Comparing those two runners without converting first would make them look far apart when they are only about 13 seconds per kilometre different.
Common mistakes to avoid
Reading decimals as seconds. A result of 6.5 minutes per km is 6:30, not 6:50, because 0.5 of a minute is 30 seconds. Multiply the decimal part by 60 to get the seconds.
Comparing numbers in different units. A 9:39 mile pace and a 6:00 km pace are the same run. Always check whether a plan, an app or a friend is talking per mile or per kilometre.
Forgetting where speed comes from. Your speed is simply your cadence (steps per minute) multiplied by your stride length. At, say, 160 steps per minute with a 1 metre stride, you cover 160 metres per minute, or 9.6 km/h, roughly a 6:15/km pace. Getting faster means improving one or both, gradually.
If you would rather skip the arithmetic, enter your distance and time in our pace calculator and it will give you your pace instantly.
