Convert inches to mm

Inch

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

Ursprung
The name “inch” comes from the Latin uncia, meaning “one-twelfth.” Early measures tied an inch to three barleycorns laid end-to-end or the average width of three thumbs. Later, it was standardized against the international yard.

Modern användning
Today, inches are the standard for carpentry, hardware dimensions, and screen sizes in the U.S., Canada, and U.K. They also appear worldwide for electronics (TV and smartphone diagonals).

Millimeter

Definition
A millimeter (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.

Ursprung
The prefix milli- (Latin mille “thousand”) indicates 10⁻³. While the meter was once defined by a metal bar, today it’s tied to the speed of light—yet the link (1 mm = 0.001 m) remains constant.

Modern användning
Millimeters are essential for engineering tolerances, technical drawings, machining parts, and precise measurements in science and manufacturing.

Inch → Millimeter Conversion Table

Hur man konverterar

• 1 in = 25.4 mm

• 1 mm = 0.03937 in

Exempel

Convert 15 in to millimeters:

15 in × 25.4 mm/in = 381 mm