Convert cm to mm

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 provides a convenient subdivision of the meter for finer measurements.

起源
Formed from the prefix センチ (ラテン語 センタム, “hundred”) and “meter,” the centimeter fits into the metric system’s base-10 architecture, where prefixes from キロ (10³) down to ナノ (10⁻⁹) make scaling seamless.

現代の使用
Centimeters are used worldwide wherever a smaller unit than the meter is needed: measuring heights, small objects, and classroom rulers—especially outside the United States where metrication is standard.

ミリメートル

定義
A millimeter (symbol: mm) is an SI unit of length equal to one-thousandth of a meter (0.001 m). It corresponds to the distance light travels in 1/299 792 458 000 of a second, inheriting the meter’s exactness.

起源
The ミリ prefix (Latin ミル, “thousand”) indicates 10⁻³. Although the meter’s realization has shifted—from a physical bar to a light-based constant—the fixed link (1 mm = 0.001 m) remains unchanged.

現代の使用
Millimeters are essential for engineering tolerances, technical drawings, machining parts, and any situation demanding high precision.