If your address is in the United States, Myanmar or Liberia, you're living in one of the only three countries in the world that still use the British Imperial system of measurement. You're used to expressing your height in feet and inches, but when you're talking to someone who lives in a country that uses the metric system, which is every other country but those three, the information will be more useful if you convert it to meters or -- better yet -- centimeters. The conversion isn't complex, but you may need your calculator.
TL;DR (Too Long; Didn't Read)
TL;DR: To convert feet to meters, multiply by 0.305, and to convert from inches to centimeters, multiply by 2.54. Add them together to get your height in metric units.
Units of Length in the Imperial and Metric Systems
The basic units for length in the Imperial system are based on imprecise standards. King Charlemagne ruled France in the 8th century, and a foot was originally defined as the length of his foot. It was later modified to be the length of 36 barleycorns laid end to end. The inch was originally the width of the thumb of King Edgar, who ruled Britain in the 10th century.
The meter, on the other hand, was originally defined as one ten-millionth of the distance from Earth's equator to its pole. Today, scientists define it with reference to a length marked on a standard bar kept at the International Bureau of Weights and Measures near Paris. This current measurement has represented both 1,650,763.73 wavelengths of orange-red light, emitted by the krypton-86 atom, and 1/299,792,458 of the distance it takes for light to travel in one second through a vacuum. A centimeter is defined as one one-hundredth of a meter.
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Making the Conversion
Converting between feet and meters is straightforward:
1 meter = 3.28 feet; 1 foot = 0.305 meters.
To make the conversion between inches and centimeters, you need these conversion factors:
1 inch = 2.54 centimeters; 1 centimeter = 0.394 inches.
Using this information, you can convert your height in a two-step process. First convert the number of feet to meters, and then convert the number of inches to centimeters. Since a centimeter is one one-hundredth of a meter, you can express it as a two-place decimal and add it to the number of meters.
George is 5'8" tall. First convert the feet to meters: 5 ft. • .305 = 1.53 meters. Now convert the inches to centimeters: 8 in. • 2.54 = 20.32 centimeters = 0.20 meters. Add these together to get 5'8" = 1.73 meters.
The convention in metric countries is to express height in centimeters. Using this convention, George's height is 173 cm. It's easier to convert to centimeters if you first convert the height to inches. For example, George's height is (5 • 12 + 8) = 68 inches. Now you need only multiply by 2.54 to get George's height in centimeters: 68 in. • 2.54 = 173 cm.