Convert mph to km/h
Miles per hour convert to kilometers per hour with a single multiply by 1.60934 — a pure proportional scaling with no offset.
- Meter/Second (m/s)0.44704
- Kilometer/Hour (km/h)1.609344
- Mile/Hour (mph)1
- Knot (knot)0.868976
🔒 Unit conversions are computed in your browser.
The exact formula
Converting miles per hour to kilometers per hour takes a single multiplication: km/h = mph × 1.60934. The constant comes straight from the definition of a mile as exactly 1.609344 kilometers. Because speed is a proportional quantity, there's nothing to add or subtract — 0 mph is 0 km/h. That's what separates it from temperature: Fahrenheit to Celsius is an affine conversion with a −32 offset, but here you only ever scale. To go the other way, multiply km/h by 0.621371.
Worked examples with real speeds
A US highway limit of 60 mph works out to 60 × 1.60934 = 96.56 km/h. A common interstate 70 mph is 112.65 km/h, and the UK's 30 mph urban limit is 48.28 km/h. A 100 mph fastball translates to 160.93 km/h. For a quick dashboard estimate you can just multiply by 1.6, but that shortcut runs about 0.58% low: 100 mph × 1.6 gives 160 km/h, roughly 0.9 km/h under the true value.
Rounding, knots, and regional units
The mental shortcut 1 mph ≈ 1.6 km/h is fine for a ballpark, but use 1.60934 whenever precision matters — the error grows with speed. Don't confuse mph with knots, either: one knot is 1.852 km/h, a different unit used in aviation and at sea. Regions differ too. Road signs in the US and UK are posted in mph, while most of the world, including Korea, uses km/h. If you import a US car or rent one abroad, check which unit the speedometer shows.
Frequently asked questions
What is 60 mph in km/h?
60 mph equals 96.56 km/h (60 × 1.60934 = 96.5604). It's a typical US highway speed. A quick mental estimate of 60 × 1.6 = 96 km/h gets you close, but the precise figure is 96.56 km/h.
Is there an easy way to convert mph to km/h in my head?
Multiply by 8/5, which is 1.6 — for example, 50 mph is 50 ÷ 5 × 8 = 80 km/h. Because the true factor is 1.60934, the 1.6 shortcut lands about 0.58% low. At city speeds the gap is under 1 km/h and safe to ignore; at highway speeds, use the converter above for the exact number.
Do I ever add or subtract anything, like with temperature?
No. Speed is a purely proportional conversion — just multiply. Fahrenheit to Celsius is affine because of its (°F − 32) offset, but mph to km/h maps zero to zero, so 1.60934 is the only number you need. Every speed converts with one multiplication and no offset.