42 miles per hour to kilometers per hour
67.6 km/h
42 mph = 67.6 km/h.
kilometers per hour
67.6km/h
42 mph = 67.6 km/h
The short answer
How many kilometers per hour is 42 miles per hour?
42 mph = 67.6 km/h. 1 miles per hour = 1.609344 kilometers per hour, so the working is 42 × 1.609344 = 67.6.
The working
The factor below is an exact definition rather than a measurement, so nothing is approximated in the arithmetic. The only rounding on this page happens where a number is displayed.
1 miles per hour = 1.609344 kilometers per hour 42 × 1.609344 = 67.6
How much precision do you need?
Each row is the same answer cut at a different number of decimals, with what that choice costs you. Pick the shortest row whose error is smaller than whatever you are measuring with.
| Rounded to | Answer (km/h) | Off by |
|---|---|---|
| Whole number | 68 | +0.40755 |
| 1 decimal | 67.6 | +0.00755 |
| 2 decimals | 67.59 | −0.00245 |
Round trip: take 67.6 km/h back the other way and you land on 42.0047 mph — a drift of 0.0047 mph. That gap is the rounding, not the conversion.
Frequently asked questions
What is 42 miles per hour in kilometers per hour?
42 miles per hour is 67.6 kilometers per hour. 1 miles per hour = 1.609344 kilometers per hour, so the working is 42 × 1.609344 = 67.6.
How accurate is 67.6 km/h?
Rounding to 67.6 km/h and converting straight back gives 42.0047 mph, a drift of 0.0047 mph from the 42 you started with. The factor itself is exact; every bit of that difference comes from the rounding, not the conversion.
Nearby values
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MPH to KM/H Converter
Miles per hour to kilometers per hour, with the speed limits you will actually meet.
Open the mph to km/h converter →