Speed Converter
Convert speed units — km/h, mph, m/s, knots and ft/s.
1 km/h =
0.621371 mph
How to use
- Type the value to convert — decimals are fine.
- Pick the current unit on the left and the target unit on the right. The middle button swaps direction.
- The result updates as you type. Check the conversion table and formula below, too.
Frequently asked questions
How accurate are the results?+
Calculations use the internationally standardized (SI) definitions; only the display is rounded to about six significant digits. That's plenty for everyday, school and work use.
How fast is 65 mph in km/h?+
65 mph ≈ 104.6 km/h. Multiply mph by 1.6 for a quick km/h estimate — handy for reading US speed-limit signs.
What is a knot?+
The speed unit of ships and aircraft: 1 knot = one nautical mile per hour = 1.852 km/h. Storm wind speeds are often given in knots, too.
Does it need a fast connection?+
No. The math runs instantly inside your browser with no server round-trip — it even works offline once the page is open.
Is it really free?+
Yes. No sign-up, no install, no usage limits. The site is ad-supported.
Unit guide
Why so many speed units
Roads use km/h (most countries) or mph (US, UK); sea and air use knots; science and sports use m/s. Anchors: 100 km/h ≈ 62 mph, 10 m/s = 36 km/h (a sprinter), 20 knots ≈ 37 km/h (a fast ferry).
How this converter calculates
Every unit is converted to km/h first, then divided into the target unit, using the exact definitions of the mile (1.609344 km) and nautical mile (1.852 km).