# 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
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.

### Unit of measurement

unitunits of measurementweights 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.

### Length

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.

### Equality (mathematics)

equalityequalequalities
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.

### SI base unit

base unitSI base unitsbase units
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.

### 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

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### Japanese language

JapaneseJapanese-languageJp

### Korean language

KoreanKorean-languageKorea

### CJK characters

CJKCJK encodingCJK character

### Unicode

Unicode StandardUnicode Transformation FormatThe Unicode Standard