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Miles per Hour to Kilometres per Hour

Convert speeds and limits between mph and km/h.

Inputs
mph

The number of miles per hour to convert.

Kilometres per hour
112.65km/h
In metres per second
31.29m/s
20 mph
32.19km/h
30 mph
48.28km/h
60 mph
96.56km/h
70 mph
112.65km/h
km/h = mph × 1.609344

1 mph = 1.609344 km/h

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Multiply mph by 1.609344 to get km/h. A 70 mph motorway limit is 112.65 km/h, which is why converted limits never look like round numbers — each country sets round figures in its own unit.

How to use MPH to KM/H Converter

  1. Enter the value. Decimals are fine.
  2. Read the conversion. A short reference table is shown for the values that come up most.

About converting mph to km/h

Speed conversion is straightforward arithmetic wrapped around a practical oddity: no country signs a converted limit. Limits are chosen as round numbers in the local unit, so 30 mph and 50 km/h are both "the urban limit" despite being 1.8 km/h apart, and 70 mph and 120 km/h are both "the motorway limit" despite a gap of nearly eight. Converting a limit therefore tells you what the sign means, not what the neighbouring country would have written. The other practical point concerns the instrument rather than the unit. Type approval rules in the EU, UK and most other markets require that a speedometer never indicate less than true speed, and permit it to over-read by a margin — commonly around ten percent plus a few km/h. Manufacturers use that allowance, so a dial reading 70 typically corresponds to something nearer 66 or 67. GPS-derived speed, which is what a phone or satnav shows, is generally much closer to the truth, and the persistent discrepancy between the two is a feature of the regulation rather than a fault. Metres per second is worth having alongside for anything involving physics, since it is the SI unit and the one every formula expects.

Frequently asked questions

What is 70 mph in km/h?
112.65 km/h. No country signs that figure, because limits are set as round numbers in whichever unit is local — which is why 70 mph and 120 km/h coexist as "the motorway limit" despite being 7 km/h apart.
What is the quick mental conversion?
Add sixty percent: half again plus a tenth. 60 mph becomes 60 + 30 + 6 = 96, against the true 96.6. It is accurate to about half a percent, which is well within the tolerance of any speedometer.
Why does my speedometer read high?
Because regulations in most markets require that it never reads below actual speed, so manufacturers bias it upward by a few percent. GPS speed is usually the more accurate figure, which is why a satnav consistently shows less than the dial.
Are knots the same as mph?
No. A knot is one nautical mile per hour, which is 1.852 km/h or about 1.151 mph. Aviation and marine speeds use knots, so an aircraft speed cannot be converted with this factor.

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