Convert inches to cm

インチ

定義
An inch (symbol: in) is a length unit in the Imperial and U.S. customary systems. Since 1959 it’s defined as exactly 25.4 mm. There are 12 inches in a foot and 36 inches in a yard.

起源
The name “inch” traces back to the Latin ウンシア (“one-twelfth”), originally denoting one-twelfth of a Roman foot. Early measures included three barleycorns end-to-end or the average width of three thumbs, before standardizing via the international yard.

現代の使用
Inches remain the default in the United States, Canada, and the U.K. for construction, hardware dimensions, and screen diagonals. They also appear in electronics globally (e.g., monitor and smartphone sizes).

センチメートル

定義
A centimeter (symbol: cm) is an SI unit of length equal to one-hundredth of a meter (0.01 m). It belongs to the metric system’s straightforward decimal framework.

起源
プレフィックス センチ (ラテン語 センタム “hundred”) plus “meter,” the centimeter forms part of the metric family of prefixes—from キロ (10³) to nano- (10⁻⁹)—facilitating easy scaling.

現代の使用
Centimeters are used worldwide wherever a finer division of the meter is needed: measuring height, small objects, school rulers, and many scientific applications outside the U.S.