The meter is the basic unit of length in the SI system of units. The meter is defined to be the distance light travels through a vacuum in exactly 1/299792458 seconds. An interesting effect of the definition of the meter this way is that it fixes the speed of light in a vacuum to the exact value of 299,792,458 m/s. The previous definition of the meter was one ten-millionth of the distance from the geographic north pole to the equator, measured over the earth's surface in a circle running through Paris, France. Meters are abbreviated using a lower case "m" in measurements.

1 m is about 39.37 inches. This is a bit more than one yard. There are 1609 meters in a statute mile. Prefix multipliers based on powers of 10 are used to convert meters to other SI units. For example, there are 100 centimeters in a meter. There are 1000 millimeters in a meter. There are 1000 meters in a kilometer.

### An Example

A meter is any device which measures and records the quantity of a substance. For example, a water meter measures the volume of water. Your phone measures the amount of digital data that you use.

### An Electrical or Magnetic Quantity

A meter is any device which measures and may record an electrical or magnetic quantity, such as voltage or current. For example, an ammeter or voltmeter are kinds of meters. Use of a such a device may be termed "metering" or you might say the quantity being measured is being "metered".

Aside from knowing what a meter is, if you're dealing with the unit of length, you need to know how to convert between it and other units.

### Yard to Meter Unit Conversion

If you use yards, it's good to be able to convert the measurement to meters. A yard and a meter are close to the same size, so when you get an answer, check to make sure the values are close. The value in meters should be slightly less than the original value in yards.

1 yard = 0.9144 meters

So if you want to convert 100 yards to meters:

100 yards x 0.9144 meters per yard = 91.44 meters

### Centimeter to Meter (cm to m) Conversion

Most of the time, length unit conversions are from one metric unit to another. Here's how to convert from cm to m:

1 m = 100 cm (or 100 cm = 1 m)

Say you want to convert 55.2 centimeters to meters:

55.2 cm x (1 meter / 100 cm) = 0.552 m

Make sure the units cancel out and leave the one you want on "top". So centimeters cancel and meters is on top.

### Converting Kilometers to Meters

The kilometer to meter conversion is common.

1 km = 1000 m

Say you want to convert 3.22 km into meters. Remember, you want to make sure the desired unit remains in the numerator when you are canceling units. In this case, it's a simple matter:

3.22 km x 1000 m/km = 3222 meters