An inch is a small unit of length: it equals exactly 2.54 centimeters, or about 25.4 millimeters.

Quick Scoop

Basic definition

  • 1 inch = 2.54 cm exactly.
  • That’s 0.0254 meters, or about the width of a standard adult thumb at the knuckle.
  • In older imperial terms, an inch is 1/12 of a foot and 1/36 of a yard.

How to picture an inch

You can imagine an inch using everyday objects:

  • The width of an average adult thumb across the knuckle is roughly 1 inch.
  • Many standard shirt buttons or the thickness of a typical pencil eraser are close to an inch across.
  • On a ruler, one inch is the distance between two large numbered marks, usually divided into smaller lines (1/2, 1/4, 1/8, etc.).

Metric comparison

  • 1 inch ≈ 2.54 cm.
  • 2 inches ≈ 5.08 cm, 3 inches ≈ 7.62 cm, and so on (just multiply inches by 2.54).

Example:
If something is 5 inches long, that’s 5×2.54=12.75×2.54=12.75×2.54=12.7 cm.

TL;DR: An inch is the distance of 2.54 cm, about the width of your thumb at the knuckle, and there are 12 inches in a foot.

Information gathered from public forums or data available on the internet and portrayed here.