Speed Converter

This page converts a speed from one unit into another. Every value passes through the metre per second, the SI unit speed is held in, and speed stays speed: a unit only converts inside its own dimension.

How do you convert a speed between km/h, mph, metres per second and knots?

Pick the unit you have, pick the unit you want, and type the value. The page multiplies by the factor between the two and prints the arithmetic under the result, so the answer and the working are the same object.

1. Choose the unit your value is in. This page opens on the mile per hour.
2. Choose the unit you want it in. This page opens on the kilometre per hour.
3. Type the value. The result and the factor behind it appear together.
4. Read the working. It converts into the metre per second first and out again, which is the same two lines you would write by hand.

Speed Conversion Table

One row per unit this page offers, each measured against the metre per second. The last column says whether the factor is a definition or a reading of one.

Worked Examples

The question the bank ranked highest for this page, answered with the working.

Where These Factors Come From

Every number above is read from the knowledge base rather than computed for the page. These are the statements it holds for speed.

• One mile per hour is exactly 0.44704 m/s and one kilometre per hour is exactly 1/3.6 m/s. One knot is one nautical mile per hour, and the nautical mile is exactly 1852 m.
• An exact factor is a definition rather than a measurement. 1 in = 25.4 mm and 1 lb = 0.45359237 kg were fixed by the 1959 international yard and pound agreement, so they never gain another digit.
• Pace is time per distance and speed is distance per time, so each is the reciprocal of the other. A pace of 5 min/km is a speed of 12 km/h, because 60 / 5 = 12.
• The international nautical mile is exactly 1852 m. It is a different unit from the statute mile of 1609.344 m and is used for distance at sea and in the air.
• How this page reports a result result in the target speed unit, plain decimal

What Is a Knot, and Why 1852 Metres?

A knot is one nautical mile per hour, and the international nautical mile is a defined length rather than a measured one. That is why a knot converts into metres per second through a factor that is exact, and why the result names the unit it was measured in.

The rule behind this factor is the same for every unit - which way round the factor goes.

Frequently Asked Questions

Related Conversions

• Pressure sits in the same measurement group as speed - pressure in pascals, bar and atmospheres.
• Mass sits in the same measurement group as speed - the mass factor table.
• Torque sits in the same measurement group as speed - convert torque between newton-metres and pound-feet.
• Pace sits in the same measurement group as speed - convert a running pace between minutes per kilometre and minutes per mile.
• If you are measuring volumetric flow rate rather than speed, the volumetric flow rate factors instead.
• If you are measuring power rather than speed, convert power between watts and kilowatts instead.

The rest of the family sits on all the unit converters.