40 Miles per hour to Kilometres per hour (40 mph to km/h)
40 Miles per hour equals 64.3738 Kilometres per hour. Below is the formula, the worked arithmetic, and what 40 mph typically represents in everyday use.
Formula and worked answer
Formula
km/h = mph × 1.609344
Substituting 40 for mph: 40 × 1.609344 = 64.3738 km/h. The factor 1.609344 comes from the exact international definition of the Mile per hour relative to the Kilometre per hour, so this answer is precise rather than rounded.
What does 40 Miles per hour represent?
40 mph (64.37 km/h) is a common US arterial-road speed limit and the figure US driving-school textbooks use as the reaction-distance reference for stopping calculations. Converted to metric the figure is 64.37 km/h, which European jurisdictions typically round to either 60 km/h on equivalent arterials or 70 km/h on slightly faster roads. The 4.37 km/h gap between the US 40 mph limit and the European 60 km/h limit is enough that an American driver at "40 mph" is technically over the equivalent European limit by about 7%, which is why European telematics dashboards configured to score a 40-mph US driver flag them at the higher European tier of the speeding-band scoring rubric.
Values near 40 mph
- 35 mph=56.327 km/h
- 36 mph=57.9364 km/h
- 37 mph=59.5457 km/h
- 38 mph=61.1551 km/h
- 39 mph=62.7644 km/h
- 41 mph=65.9831 km/h
- 42 mph=67.5924 km/h
- 43 mph=69.2018 km/h
- 44 mph=70.8111 km/h
- 45 mph=72.4205 km/h
mph to km/h reference table around 40
| mph | km/h |
|---|---|
| 20 mph | 32.1869 km/h |
| 30 mph | 48.2803 km/h |
| 35 mph | 56.327 km/h |
| 39 mph | 62.7644 km/h |
| 40 mph | 64.3738 km/h |
| 41 mph | 65.9831 km/h |
| 45 mph | 72.4205 km/h |
| 50 mph | 80.4672 km/h |
| 60 mph | 96.5606 km/h |
| 80 mph | 128.7475 km/h |
Convert a different value
Looking for a different number of Miles per hour? Use the full mph to km/h converter to enter any value, see the worked formula, and read the full background on the Mile per hour and the Kilometre per hour. To go the other direction, the km/h to mph converter applies the inverse factor and is the page to bookmark if you usually start in Kilometres per hour.