Speed Converter (m/s, km/h, mph, knots)

Understanding the speed converter — concept and principle

This converter changes a speed between kilometres per hour (km/h), miles per hour (mph), metres per second (m/s), knots and feet per second. Use it when driving abroad or renting a car with a mph speedometer, reading wind speed in a weather forecast, following boating or aviation figures in knots, or doing physics homework in m/s.

1 mph is exactly 1.609344 km/h, so 60 mph reads about 96.6 on the km/h scale.

How it is calculated

The value is converted to km/h and then divided by the size of the target unit: result = value × (km/h per "from" unit) ÷ (km/h per "to" unit). The factors are exact:

1 mph = 1.609344 km/h, because the international mile is exactly 1,609.344 m.
1 m/s = 3.6 km/h, because an hour has 3,600 s.
1 knot = 1.852 km/h, because the international nautical mile is exactly 1,852 m.
1 ft/s = 1.09728 km/h, because a foot is exactly 0.3048 m.

The principle

Speed is distance divided by time, so converting it means converting the distance unit and the time unit together. The mile and foot have been defined in metres since the 1959 international yard and pound agreement, and the nautical mile was set at 1,852 m by international convention; it originally approximated one minute of latitude, which is why ships and aircraft use it with charts. Since every factor is a defined value, the conversions are exact, and only the display is rounded.

Worked example

Default inputs: 60 mph converted to km/h.

Multiply by the factor: 60 × 1.609344 = 96.56064 km/h.
In m/s: 96.56064 ÷ 3.6 = 26.8224 m/s.
In knots: 96.56064 ÷ 1.852 = 52.1386 knots.
In ft/s: 96.56064 ÷ 1.09728 = 88 ft/s.
Result: 60 mph = 96.56064 km/h.

How to read the result

Quick mental rules: km/h ≈ mph × 1.6, mph ≈ km/h × 0.62, km/h ÷ 3.6 = m/s, and one knot is a little more than 1.85 km/h. For orientation, 30 mph is about 48 km/h and 70 mph about 113 km/h. Walking is about 5 km/h (1.4 m/s), and a strong wind of 20 m/s is 72 km/h. On the road, always follow the units of the signs in the country you are driving in.

Common mistakes

Rounding the mile to 1.6 km for exact work; 100 km/h is 62.14 mph, not 62.5.
Dividing by 3.6 the wrong way: m/s to km/h means multiplying by 3.6.
Confusing a knot (nautical mile per hour) with a statute mile per hour.
Writing "knots per hour"; a knot already includes "per hour".

Keep in mind: Speedometers have their own tolerances and usually read slightly high, so a converted value does not guarantee legal compliance. Observe local speed limits.

FAQ

Frequently asked questions

How many km/h is 60 mph?

Exactly 96.56064 km/h, about 97 km/h.

How fast is 100 km/h in mph?

About 62.14 mph.

How many km/h is one knot?

Exactly 1.852 km/h, about 0.514 m/s.

Sources: NIST Special Publication 811 (2008), Appendix B, conversion factors · BIPM, The International System of Units (SI Brochure), 9th edition, 2019

Checked 8 Nov 2026. Factors from the SI Brochure (BIPM, 9th ed.) and NIST Special Publication 811 (2008), Appendix B.