Inches to mm Conversion (Inches To Millimeters) - Inch Calculator (2024)

For example, here's how to convert 5 inches to millimeters using the formula above.

millimeters = (5" × 25.4) = 127 mm

What Is an Inch?

An inch is a unit of length equal to ¹/₁₂ of a foot or ¹/₃₆ of a yard.Because the international yard is legally defined to be equal to exactly 0.9144 meters, one inch is equal to 2.54 centimeters.^[2]

The inch is a US customary and imperial unit of length. Inches can be abbreviated as in; for example, 1 inch can be written as 1 in.

Inches can also be denoted using the ″ symbol, otherwise known as a double-prime.Often a double-quote (") is used instead of a double-prime for convenience.A double-prime is commonly used to express 1 in as 1″.

The standard ruler is 12 inches long and is a common tool for measuring a length in inches.Another frequently used tool to perform measurements in inches is a tape measure, which commonly comes in lengths from 6' - 35'.Other types of devices used to make measurements in inches include scales, calipers, measuring wheels, micrometers, yardsticks, and even lasers.

Learn more about inches.

What Is a Millimeter?

One millimeter is equal to one-thousandth (1/1,000) of a meter, which is defined as the distance light travels in a vacuum in ¹/_299,792,458 of a second.One millimeter is equal to 0.0393701 inches.

The millimeter, or millimetre, is a multiple of the meter, which is the SI base unit for length. In the metric system, "milli" is the prefix for thousandths, or 10^-3. Millimeters can be abbreviated as mm; for example, 1 millimeter can be written as 1 mm.

Millimeters are often represented by the smallest ticks on most metric rulers.To get a reference point of the size, the thickness of a US dime is 1.35mm.^[3]

Learn more about millimeters.