How to convert from centimeters to inches
Divide by 2.54. An inch has been defined as exactly 2.54 cm since 1959, so this one never drifts – 30 cm comes to 11.81 inches, which is why a 30 cm ruler falls just short of a foot.
For a rough answer in your head, multiply by 4 and divide by 10: 30 cm gives 12 inches, about 1.6% high. Fine for a shelf, less so for a sewing pattern where the error adds up seam by seam.
Centimeters
A centimeter (cm) is one hundredth of a meter, and there are exactly 2.54 of them in an inch. The prefix centi- is from the Latin for a hundred.
Clothing sizes, heights and paper are in centimeters in most of the world – an A4 sheet is 21cm by 29.7cm and a new pencil is about 19cm.
100 centimeters make a meter and 100,000 make a kilometer, so conversions within the metric system are a matter of moving the decimal point.
What are inches?
Inches are mainly used in the United States as well as sometimes in the United Kingdom.
An inch is 1/12th of a foot, or exactly 2.54 centimeters. It is divided into fractions rather than decimals – halves, quarters, eighths – so a new pencil is about 7½ inches rather than 7.5.
To convert inches to centimeters multiply by 2.54, so 100 inches is 254 centimeters. To convert centimeters to inches divide by 2.54, so 50 centimeters is about 19.69 inches.
Which countries use centimeters?
A majority of countries worldwide have adopted the metric system and as such use centimeters.
In these countries millimeters are the preferred unit for measuring dimensions of building materials, such as pipes, beams, and panels. Centimeters are found in manufacturing, machinery and tools. Centimeters are also used in medicine and are used in the fashion and textile industry.
Which countries use inches?
The United States is the most notable country that uses inches but a large number of people still use them in the United Kingdom as well. In the US, inches are the standard in construction and engineering. Inches are also common in determining a person's height or the size of television screens.
Although the UK has officially adopted the metric system, inches are still found in certain area particularly in construction. This is due to the historical influence of the imperial system. In the UK inches are also used for body height and objects that were traditionally measured this way such as vinyl records.