Per mille (from Latin per mīlle 'in each thousand')^[1] is parts per thousand.^[2] Other recognised spellings include per mil,^[2] per mill,^[1][3] permil,^[1] permill,^[1] or permille.^[4][5]

The associated sign is written ‰, which looks like a per cent sign % with an extra zero or o in the divisor.

Major dictionaries do not agree on the spelling^[1][2][3] and some dictionaries, such as Macmillan,^[6] do not even contain an entry. One common usage is blood alcohol content, which is usually expressed as a percentage in English-speaking countries.

Per mille should not be confused with parts per million (ppm).

Computer systems

The code point for the glyph is included in the General Punctuation block of Unicode characters: U+2030 ‰ PER MILLE SIGN.^[4] It may be typed using Alt+0137, Compose%o, Ctrl+⇧ Shift+u 2030, or ⌥ Option+⇧ Shift+r according to operating system.

Note that for the compose key sequence the percent key (%) is followed by lower case letter o and not, as might be expected, by digit 0.^[7]

Examples

Examples of use include:

• Legal limits of blood-alcohol content for driving a road vehicle in some countries: for example: 0.5‰ or 0.8‰.
• 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‰".
• Fineness of precious metals.
• Cost per mille (CPM), the price of 1000 units, may be used for views of banner and display advertising, and for emails delivered by email service providers.

Related units

• Percentage point difference of 1 part in 100
• Percentage (%) 1 part in 100
• Basis point (bp) difference of 1 part in 10,000
• Permyriad (‱) 1 part in 10,000
• Per cent mille (pcm) 1 part in 100,000