Convert Miles per Hour to Kilometers per Hour
Miles per hour to kilometers per hour is the conversion you need whenever a speed shows up in the imperial system but you think — or drive — in metric. One mph is exactly 1.609344 km/h, so the number always gets bigger when you switch from mph to km/h.
Miles per hour to Kilometers per hour conversion table
| Miles per hour (mph) | Kilometers per hour (km/h) |
|---|---|
| 1 | 1.609344 |
| 2 | 3.218688 |
| 3 | 4.828032 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 20 | 32.18688 |
| 50 | 80.4672 |
| 100 | 160.9344 |
| 500 | 804.672 |
| 1,000 | 1,609.344 |
The formula
To convert miles per hour to kilometers per hour, multiply the speed in mph by 1.609344:
kilometers per hour = miles per hour × 1.609344
A worked example
Say a car is traveling at 70 mph on the highway and you want to know that speed in km/h:
70 × 1.609344 = 112.65 km/h
That's why a 70 mph speed limit in the US corresponds to roughly a 113 km/h limit on a metric speedometer.
Why the number is exact
Miles per hour and kilometers per hour come from two different measurement systems, but the units underneath them are tied together precisely: one international mile is defined as 1609.344 metres exactly. Because both units measure the same one-hour time span, that exact distance relationship carries straight through to speed, making every mph-to-km/h conversion exact rather than an approximation.
When you'll use it
Reading foreign speed limits and car speedometers, comparing top speeds between US and international car specs, and converting cycling or running pace data that mixes imperial and metric units.
Frequently asked questions
How many kilometers per hour are in a mile per hour?
Exactly 1.609344 km/h. This isn't a rounded estimate — it follows directly from the exact definition of the mile, so the conversion is precise every time.
Is the mph to km/h conversion exact?
Yes. Since 1959 the international mile has been defined as exactly 1609.344 metres, so multiplying a speed in mph by 1.609344 gives an exact answer in km/h — any rounding you see is only in how the result is displayed.
What's a quick way to estimate mph to km/h in my head?
Add roughly 60%. A 60 mph speed limit is close to 97 km/h; a 100 mph top speed is close to 161 km/h. For anything that matters, use the exact factor above.