Per mille

‰
Per mille

Visualisation of 1%, 1‰, 1‱ and 1 ppm as the fraction of the red cube to its respective block (click for larger version)

A per mille^[1][2][3] (from Latin per mīlle, "in each thousand"^[4]), also spelled per mil,^{[1][2][4][5][6][7]} per mill,^{[4][5][6][7][8][9]} permil,^[4] permill,^[4] or permille^[3] is a sign indicating parts per thousand. Per mil should not be confused with parts per million (ppm).

The sign is written ‰, which looks like a percent sign (%) with an extra zero in the divisor. It is included in the General Punctuation block of Unicode characters: U+2030 ‰ PER MILLE SIGN (HTML ‰ · ‰).^[3] It is accessible in Windows using ALT+0137.

The term occurs so rarely in English that major dictionaries do not agree on the spelling or pronunciation even within a single dialect of English^[10] and some major dictionaries such as Macmillan^[11] and Longman^[12] do not even contain an entry. The term is more common in other European languages where it is used in contexts, such as blood alcohol content, that are usually expressed as a percentage in English-speaking countries.

Examples

A railroad distance and gradient sign in the Czech Republic. The 20‰ grade is equivalent to 2%.

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)

Related units

• Percentage point
• Percent (%) 1 part in 100
• Basis point (‱) 1 part in 10,000
• Parts-per notation
• Silver fineness (given as "0.000-fine")

References

1. Cambridge Dictionary Online. "per mille". Cambridge University Press (Cambridge), 2014. Accessed 31 August 2012.
2. Oxford Dictionaries: The British & World Dictionary. "per mille" Accessed 1 Aug 2014.
3. Unicode. "General Punctuation". 2014. Accessed 5 Aug 2014.
4. Oxford English Dictionary, 3rd ed. "per mil, adv." Oxford University Press (Oxford), 2005.
5. eReference. "per mil". Houghton Mifflin. Accessed 31 Aug 2012.
6. Oxford Dictionaries: The American Dictionary. "per mill". Accessed 1 Aug 2014.
7. Collins English Dictionary. "per mill or per mil". 2014. Accessed 1 Aug 2014.
8. Merriam–Webster Online. per mill". Accessed 1 Aug 2014.
9. Collins American English Dictionary. "per mill". 2014. Accessed 1 Aug 2014.
10. See entries above
11. Macmillan Dictionary. "No result". Accessed 1 Aug 2014.
12. Longman Dictionary of Contemporary English. "No result". Accessed 1 Aug 2014.