A per mil or per mille (also spelled permil, permille, per mill or promille) (Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

, literally meaning 'for (every) thousand') is a tenth of a percent or one part per thousand. It is written with the sign ‰ (Unicode

Unicode

Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

 U+2030, html entity ‰), which looks like a percent sign

Percent sign

The percent sign is the symbol used to indicate a percentage .Related signs include the permille sign ‰ and the permyriad sign , which indicate that a number is divided by one thousand or ten thousand respectively...

 (%) with an extra zero at the end. It can be seen as a stylized form of the three zeros in the denominator, although it originates from an alteration of the percent sign.

A per mil is defined as:

1‰ = 10⁻³= = 0.001 = 0.1%

1% = 10‰

A per mil should not be confused with ppm

Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

 (commonly pronounced "parts per million" in the United States). A measurement in ppm means parts per million, and has as its denominator 1,000,000 and not 1,000.

Examples

Examples of common use include:

• Legal limits of blood-alcohol content for driving a road vehicle in some countries are 0.5‰ or 0.2‰.
• Seawater salinity
  Salinity
  Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
  
  . For example "the average salinity is 35‰".
• Tunnel
  Tunnel
  A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...
  
   and railway gradients (in some countries)
• Birth
  Birth rate
  Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...
  
   and death rates.
• Baseball batting average
  Batting average
  Batting average is a statistic in both cricket and baseball that measures the performance of cricket batsmen and baseball hitters. The two statistics are related in that baseball averages are directly descended from the concept of cricket averages.- Cricket :...
  
  s, colloquially
• When used to describe property tax
  Property tax
  A property tax is an ad valorem levy on the value of property that the owner is required to pay. The tax is levied by the governing authority of the jurisdiction in which the property is located; it may be paid to a national government, a federated state or a municipality...
  
  ation, it is called the millage
  Property tax
  A property tax is an ad valorem levy on the value of property that the owner is required to pay. The tax is levied by the governing authority of the jurisdiction in which the property is located; it may be paid to a national government, a federated state or a municipality...
  
   rate (U.S.
  United States
  The United States of America is a federal constitutional republic comprising fifty states and a federal district...
  
  ) or mill rate (Canada
  Canada
  Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
  
  ).
• Used to describe stable-isotope
  Stable isotope
  Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...
  
   ratios. For example "δ¹³C was measured at -3.5‰"

Related units

• Percentage point
  Percentage point
  Percentage points are the unit for the arithmetic difference of two percentages.Consider the following hypothetical example: in 1980, 40 percent of the population smoked, and in 1990 only 30 percent smoked...
  
  
• Percent
  Percentage
  In mathematics, a percentage is a way of expressing a number as a fraction of 100 . It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% is equal to 45/100, or 0.45.Percentages are used to express how large/small one quantity is, relative to another quantity...
  
   (%) 1 part in 100
• Basis point
  Basis point
  A basis point is a unit equal to 1/100 of a percentage point or one part per ten thousand...
  
    1 part in 10,000
• Parts-per notation
  Parts-per notation
  In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...