Pace vs. Speed: Why Runners Use Minutes Per Mile Instead of MPH
Pace (minutes per mile or kilometer) is more directly useful for runners than speed (miles or kilometers per hour) because race distances are fixed and known in advance — pace lets a runner directly calculate an expected finish time for a specific distance, which is usually the more practically relevant question than raw speed.
This is a convention specific to running (and a few other endurance sports) that makes practical sense once the reasoning behind it is made explicit.
Why pace answers the more useful question
For a runner, the practically relevant question is almost always "how long will this race or run take" — pace directly answers that by simple multiplication (pace × distance = time), while speed requires an extra conversion step (distance ÷ speed = time) to get to the same answer.
Converting between the two
To convert pace to speed: divide 60 by the pace in minutes per mile (a 6:00/mile pace is 60 ÷ 6 = 10 mph). To convert speed to pace: divide 60 by the speed in mph (10 mph is 60 ÷ 10 = 6:00/mile). The relationship is a direct inverse, just expressed in different units.
Why cycling conventionally uses speed instead
Cycling more commonly uses speed (mph or km/h) rather than pace, partly because cycling speeds vary more dramatically with terrain and drafting than running pace typically does, making a rate-based (speed) framing more naturally intuitive for that sport — different endurance sports have settled on different conventions for practical, sport-specific reasons.