A per mil, per mille, or per mill (permil or permille) (Latin, literally meaning 'for (every) thousand') is a tenth of a percent or one part per thousand. It is written with U+2030 ‰ per mille sign (HTML:
‰) (Windows: ALT+0137), which looks like a percent sign (%) 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.
The term is so rarely used in English that major dictionaries do not agree on the spelling or pronunciation (even within one kind of English) and often do not list the other variants or do not even have an entry (for example Longman, and Macmillan). The term is very common in most other languages, for example in expressing blood alcohol content, which is usually expressed in percent in English-speaking countries.
A per mil is defined as:
- 1‰ = 10−3= 1⁄1000 = 0.001 = 0.1%
- 1% = 10‰
Examples of common use include:
- legal limits of blood-alcohol content for driving a road vehicle in some countries: for example: 0.6‰ or 0.2‰.
- seawater salinity: for example: "the average salinity is 35‰".
- tunnel and railway gradients (in some countries in Europe)
- birth and death rates
- baseball batting averages (colloquially)
- property taxation rates: the millage rate (U.S.) or mill rate (Canada)
- expressing stable-isotope ratios - for example: "δ13C was measured at −3.5‰"
- expressing costs for print and online advertisements which are commonly sold at cost per mille (CPM); this is the common unit for all banner and display advertising
- frequently used by email service providers to denominate the cost for 1,000 emails delivered as a cost per mille (CPM)
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