Speed Converter

Which speed units does the converter handle?

Speed is a distance divided by a time, so every unit is a length unit paired with a time unit. This converter covers the six that come up most often. The right-hand column gives each one in meters per second, which is the hub every conversion passes through.

Metric versus imperial speed units

Kilometers per hour is the road unit in most countries, while miles per hour is used on roads in the United States, the United Kingdom and a handful of other places. Because the mile is about 1.6 times as long as the kilometer, the same speed gives a smaller number in mph than in km/h: 100 km/h is a little over 62 mph.

Meters per second is the unit scientists prefer because it fits directly into SI formulas. Feet per second and yards per second survive in US engineering, ballistics and field-sport measurements, where distances are short. Knots belong to shipping and aviation: one knot is one nautical mile per hour, and a nautical mile (1,852 m) is tied to the geometry of the Earth rather than to a road or a foot.

How to use the converter

1. Type the speed you know into the number box in the first row.
2. Pick its unit in the list beside it.
3. Pick the unit you want in the list in the second row. The result shows up in the box next to it and updates whenever you change the number or either unit.

Results carry up to ten decimal places with trailing zeros removed, and large numbers get thousands separators. Very small results can appear in exponent form, for example 1.5e-7, which means 0.00000015.

How the conversion works

The converter first expresses your speed in meters per second and then converts that to the target unit. These are the rules for getting into and out of m/s:

• km/h to m/s: divide by 3.6. m/s to km/h: multiply by 3.6.
• mph to m/s: multiply by 0.44704. m/s to mph: divide by 0.44704.
• ft/s to m/s: multiply by 0.3048. m/s to ft/s: divide by 0.3048.
• yd/s to m/s: multiply by 0.9144. m/s to yd/s: divide by 0.9144.
• knots to m/s: multiply by 1,852 and divide by 3,600. m/s to knots: multiply by 3,600 and divide by 1,852.

speed in target = speed in source × (m/s per source unit) ÷ (m/s per target unit)Direct factors between pairs of units are listed in the table further down.

Worked examples

Each example below was worked out by hand with the factors above.

Speed conversion tables

The first table gives one unit of the row in every column unit (rounded to six decimals). To convert, multiply your number by the entry where your row meets the column you want.

What the converter does not cover

Mach number is not included. It is a ratio to the local speed of sound, which changes with air temperature and altitude (about 343 m/s at 20 °C near the ground, noticeably less in the cold air at cruising altitude), so there is no single conversion factor. The tool also converts a single speed between units; for the average speed of a trip with stops, use the average speed calculator, and to solve for a distance or a travel time try the speed, distance and time calculator.

A knot already means "nautical miles per hour", so saying "knots per hour" is a common slip that describes acceleration, not speed.

For single-pair pages with their own tables, see mph to km/h, km/h to m/s and mph to ft/s.