the.com/mph
The number your speedometer flatters and your insurance company eventually finds out about.
means Miles per hour: how many miles you'd cover in sixty minutes at your current pace.
from From the imperial mile (a thousand Roman paces, mille passus) divided by the hour, standardized as cars and cops both needed a shared language for too fast.
American holdoutMost of Earth measures speed in km/h instead.
Sound barrierRoughly 767 mph at sea level.
Sign mathMultiply mph by 1.6 for km/h.