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## Convert mm to inches calculator

## mm to inches formula

If you are frequently converting between mm and inches,it’s probably useful to know the formula to save time.

*number of mm **÷ **25.4 = number of inches*

To use the formula simply divide the number of mm by 25.4 to get the number of inches.

For example, to convert a measurementof 50.8 mm

**Number of inches = 50.8 ÷ 25.4 = 2 inches**

## mm to inches conversion table

The following table provides a quick reference for converting common mm into inches, in both decimal and fractional format.

mm |
Inches (decimal) |
Inches (fraction) |

0.01 | 0.0004 | 0 |

0.1 | 0.0039 | 0 |

1 | 0.0394 | 3/64 |

2 | 0.0787 | 5/64 |

3 | 0.1181 | 1/8 |

4 | 0.1575 | 5/32 |

5 | 0.1969 | 13/64 |

6 | 0.2362 | 15/64 |

7 | 0.2756 | 9/32 |

8 | 0.315 | 5/16 |

9 | 0.3543 | 23/64 |

10 | 0.3937 | 25/64 |

20 | 0.7874 | 25/32 |

30 | 1.1811 | 1 3/16 |

40 | 1.5784 | 1 37/64 |

50 | 1.9685 | 1 31/32 |

60 | 2.3622 | 2 23/64 |

70 | 2.7559 | 2 3/4 |

80 | 3.1496 | 3 5/32 |

90 | 3.5433 | 3 35/64 |

100 | 3.937 | 3 15/16 |

## The Global Picture

Most of the world officially use the metric system nowadays, while the USA still use imperial as the main method of measurement.

Some countries, such as the UK and other former colonies of the British Empire, use metric for most formal measurements, but still use imperial measurements informally and in specific situations: a pint of beer, measuring people’s height and weight, road signs, etc.

Other countries such asthe Philippines, South Africa, Sri Lanka, and Malaysia still use imperial units for some functions but have officially adopted the metric system.

## The Metric System (mm)

The metric system uses the Systéme International d’unités (SI units). In this system, one millimetreis equal to one-thousandthof a metre.

One metre is currently defined as the distance that light covers in a vacuum over 1/299792458000^{th} of a second. This definition was decided in 1983 at around the same time that the metric system was replacing imperial units as the preferred system of measurement around the world.

Prior to that, in 1960 one metre was defined by the number of wavelengths of a specific emission line of krypton-86.

Therefore, the precise standard definition of a metreis open to change and may be redefined again at some point in the future.

## The Imperial System (or US Customary Units) (inch)

The imperial system was adopted in 1825 across the British Empire. The United States still use US Customary Units which are very similar to imperial measurements, with one-inch being of an identical length in both systems.

Other related imperial units of length include:

**1 foot = 12 inches**

**1 yard = 36 inches**

As with most imperial measurements, the definition of one inch is believed to have come from physically measurable quantities. The earliest definition of an inch was based on the length of three dry barleycorn grains laid end-to-end. A later definition came from the average of three human thumbs.