The inch is an English unit of measure. Equals 2.54 centimeters or 25.4 milimeters. It originates in the ancient age, when the Romans measured the length with their own thumb.

Thus, the inch is the width of a regular human thumb, measured at the base of the nail. In an adult human, this measurement is approximately 2.5 cm.


The international standard symbol for inch is in (which comes from inch, inch in English). The inch unit is also represented by two single quotes, as if it were a double apostrophe (e.g. 42 "= 42 in).

The inch in our daily lives

In Brazil, the term inches is often used to specify the screen size of TV sets, computer monitors, phones, and tablets. In these cases, the measurement concerns the diagonal of the screen of the devices. For example, a 22 inch monitor would have approximately 22 * ​​2.54 = 55.88 cm diagonal.

The inch is also used on bicycle and automotive tire rims (in this case, inches represent the total diameter of the wheel).

Meet our English measurement converter.