# Millimetre

**mmmillimetermillimetersmillimetresmilimetremm*mm-мм**

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length.wikipedia

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### Metric system

**metricmetric unitsmetric unit**

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length.

Thus the kilogram and kilometre are a thousand grams and metres respectively, and a milligram and millimetre are one thousandth of a gram and metre respectively.

### Inch

**ininchesinternational inch**

Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is therfore equal to exactly 5⁄127 (≈ 0.03937) of an inch.

Standards for the exact length of an inch have varied in the past, but since the adoption of the international yard during the 1950s and 1960s it has been based on the metric system and defined as exactly 25.4mm.

### Thousandth of an inch

**milmilsthou**

This can cause confusion since in the United States, "mil" traditionally means a thousandth of an inch.

The US customary mil can be confused with the millimetre, which is the standard meaning for "mil" or "mils" (plural) in British English and European engineering circles.

### Metre

**metermmetres**

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length. Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second".

### Orders of magnitude (length)

**mm100 nmGm**

To help compare different orders of magnitude, this section lists lengths between 10 −4 m and 10 −3 m (100 μm and 1 mm).

### Submillimetre astronomy

**submillimetersubmillimeter astronomysubmillimetre**

Astronomers place the submillimetre waveband between the far-infrared and microwave wavebands, typically taken to be between a few hundred micrometres and a millimetre.

### Micrometre

**μmµmmicrometers**

One millimetre is equal to 1000 micrometres or 1,000,000 nanometres.

The micrometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known by the previous name micron, is an SI derived unit of length equalling 1 metre (SI standard prefix "micro-" = 10 −6 ); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.000039 inch).

### Centimetre

**cmcentimetercentimeters**

### American and British English spelling differences

**spelling differencesorsee spelling differences**

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length.

### International Bureau of Weights and Measures

**BIPMBureau International des Poids et MesuresInternational Bureau for Weights and Measures**

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length.

### International System of Units

**SISI unitsSI unit**

### Unit of measurement

**unitunits of measurementweights and measures**

### Length

**widthlengthsbreadth**

### Equality (mathematics)

**equalityequalequalities**

### SI base unit

**base unitSI base unitsbase units**

### Nanometre

**nmnanometernanometers**

One millimetre is equal to 1000 micrometres or 1,000,000 nanometres.

### Speed of light

**clight speedspeed of light in vacuum**

Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second".

### Vacuum

**free spaceevacuatedhigh vacuum**

Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second".

### Second

**ssecmegasecond**

Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second".

### CJK Compatibility

**CJK Compatibility (Unicode block)CJK Compatibility Unicode symbolscompatibility**

### Chinese characters

**ChineseChinese characterChinese:**

### Japanese language

**JapaneseJapanese-languageJp**

### Korean language

**KoreanKorean-languageKorea**

### CJK characters

**CJKCJK encodingCJK character**

### Unicode

**Unicode StandardUnicode Transformation FormatThe Unicode Standard**