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Italianomph to km/h: the formula and an example
To convert mph to km/h, multiply by 1.609344, the exact number of kilometers in a mile: km/h = mph × 1.609344. Example: 65 mph, a common interstate limit, is 65 × 1.609344 = 104.61 km/h.
The converter above is set to mph to km/h. The answer appears as you type, to six significant figures. The "Formula:" line shows the factor, the "In every unit" table adds meters per second and knots, and the swap button flips it to km/h to mph.
mph to km/h chart
| mph | km/h | Where you see it |
|---|---|---|
| 15 | 24.1 | School zone in many US states |
| 20 | 32.2 | UK 20 zones, most urban roads in Wales |
| 25 | 40.2 | US residential street |
| 30 | 48.3 | UK built-up area |
| 35 | 56.3 | US city arterial road |
| 40 | 64.4 | Suburban road |
| 45 | 72.4 | US suburban highway |
| 50 | 80.5 | Some UK dual carriageways |
| 55 | 88.5 | US rural two-lane road |
| 60 | 96.6 | UK national limit on single carriageways |
| 65 | 104.6 | Interstates in many states |
| 70 | 112.7 | UK motorways and dual carriageways |
| 75 | 120.7 | Rural interstates in the West |
| 80 | 128.7 | Top limit in a handful of states |
Driving abroad, speedometers, wind
Reading a km/h speedometer
Rent a car in Canada, Ireland or mainland Europe and the big numbers on the dial are km/h. To hold your usual 65 mph, aim for 105 km/h. A posted 100 km/h, the typical Canadian highway limit, is 62 mph, and 130 km/h on a French autoroute is 81 mph. Use the swap button whenever you need to go from the sign to mph.
Signs that look familiar
Speed signs abroad usually show a number in a red circle with no unit. In Ireland, which switched to metric in 2005, a "100" sign means 100 km/h, about 62 mph, not 100 mph. Northern Ireland, part of the UK, still posts mph, so watch the signs when you cross the border.
Wind speed in forecasts
Most of the world reports wind in km/h. A hurricane starts at 74 mph, which is 119 km/h, and a 40 mph gust is 64 km/h.
Mental math: add half, then a tenth
Take the speed, add half of it, then add a tenth of it. For 60 mph: 60 + 30 + 6 = 96 km/h, against an exact 96.56. That is the same as multiplying by 1.6, and it runs only 0.6% low, under 1 km/h of error up to 80 mph.
Frequently asked questions
What is 100 mph in km/h?
160.93 km/h. Going the other way, 100 km/h is 62.14 mph.
Is a knot the same as a mile per hour?
No. A knot is one nautical mile per hour, 1.852 km/h, or about 1.15 mph. Boats and aircraft use knots; the "In every unit" table shows that value too.
Why does a mile convert to exactly 1.609344 km?
Because the mile is 5,280 feet and the foot has been fixed at 0.3048 m since 1959. 5,280 × 0.3048 = 1,609.344 m, with no rounding.