MPH to KM/H Converter: Miles per Hour to Kilometers

How the mph to km/h conversion works

One mile per hour is exactly 1.609344 km/h, because one international mile is defined as exactly 1,609.344 metres. So converting mph to km/h is one multiplication: km/h = mph × 1.609344, and converting back is one division: mph = km/h / 1.609344, or km/h × 0.621371. At the default — 60 mph — the conversion is 60 × 1.609344 = 96.56 km/h, which is 60 × 0.44704 = 26.82 metres per second and 60 × 1.46667 = 88.00 feet per second. The converter works both ways: type a speed in either box and the other updates.

The worked example, line by line

Setup: speed 60 mph.

Line 1 — the conversion factor. 1 mph = 1.609344 km/h exactly, because 1 mile is exactly 1,609.344 metres.

Line 2 — kilometres per hour. 60 × 1.609344 = 96.56 km/h.

Line 3 — metres per second. 60 × 0.44704 = 26.82 m/s.

Line 4 — feet per second. 60 × 1.46667 = 88.00 ft/s.

Line 5 — the reverse. 96.56 / 1.609344 = 60.00 mph. Type the km/h and the mph comes back.

Every branch, checked

25 mph (US school zone): 25 × 1.609344 = 40.23 km/h. The most common limit a visitor to the US has to convert.

30 mph: 30 × 1.609344 = 48.28 km/h. A typical US residential speed limit.

65 mph (US highway): 65 × 1.609344 = 104.61 km/h. The standard American highway limit, just over 100 km/h.

70 mph (UK motorway): 70 × 1.609344 = 112.65 km/h. Britain’s fastest legal speed, and the one most often converted by European drivers.

100 mph: 100 × 1.609344 = 160.93 km/h. The round number that shows the factor cleanly: 100 mph is just under 161 km/h.

Reverse — km/h to mph: 50 km/h = 31.07 mph; 100 km/h = 62.14 mph; 130 km/h, the German autobahn advisory speed, = 80.78 mph.

What the defaults assume

The conversion uses the exact international definition: 1 mile = 1,609.344 metres, so 1 mph = 1.609344 km/h exactly, with no rounding in the factor itself. Metres per second uses 1 mph = 0.44704 m/s exactly, and feet per second uses 1 mph = 1.46667 ft/s (22/15, rounded at the fifth decimal). Speed limits in the table are the standard posted limits for the places named, and the German autobahn advisory speed is 130 km/h — a recommendation, not a limit, on sections without a posted maximum. Rounding convention: km/h and mph to two decimals, metres and feet per second to two decimals, all computed from unrounded values.

Output · formula · meaning

Who uses this

• The American driving in Europe: sees a 130 km/h sign on the autobahn and learns it is 80.78 mph — so they know the advisory speed is about 11 mph faster than a US highway limit, not the 130 they first feared.
• The British driver renting a car in the US: sees a 25 mph school-zone sign and learns it is 40.23 km/h — so they slow down to the speed they know, instead of guessing.
• The cyclist checking a speedometer: rides at 60 km/h and learns it is 37.28 mph — so the training log in mph and the bike computer in km/h finally agree.
• The student converting a physics problem: has 100 mph and learns it is 160.93 km/h, or 44.70 m/s — so the homework in metric units can be checked against the answer in imperial ones.

Accuracy & limitations

The math is exact for the numbers you enter: 1 mph = 1.609344 km/h by the international definition of the mile, and the reverse factor is 1 / 1.609344 = 0.621371. What the converter cannot do is read a speedometer for you, and it assumes the speed you type is a steady speed — a car that averages 60 mph over an hour has travelled 60 miles, but its speed at any moment may be higher or lower. Speed limits in the table are the standard posted limits for the places named; local limits vary, and the German autobahn advisory speed of 130 km/h is a recommendation, not a maximum, on sections without a posted limit. Read the kilometres to miles converter for the distance version of this conversion, and the speed, distance, and time calculator for travel times at a given speed.