Units of measure terms

This section covers usage and abbreviations for a variety of terms related to measurement. For other units of measure not covered here, see The Chicago Manual of Style.

  • Use numerals for measurements of distance, temperature, volume, size, weight, pixels, points, and so on—even if the number is less than 10. Add a zero before the decimal point for decimal fractions less than one, unless the customer is asked to enter the value.
    Examples
    3 ft, 5 in.
    1.76 lb
    80 × 80 pixels
    0.75 grams
    enter .75"
    3 centimeters
    3 cm

  • Insert a space between the unit of measure and the numeral, or hyphenate if the measurement modifies a noun. Examples
    13.5 inches
    13.5-inch display
    8.0 MP
    8.0-MP camera

  • Use abbreviations only with numbers in specific measurements, such as 20 MP, and don't follow the abbreviation with a period.
    Exception Follow in with a period when used as an abbreviation for inch.

  • Use commas in numbers that have four or more digits, regardless of how the numbers appear in the UI: 1,093 MB.
    Exceptions
    For years, pixels, and baud use commas only when the number has five or more digits: 1920 × 1080 pixels, 10,240 × 4320 pixels, 9600 baud, 14,400 baud.
    Don’t use commas after the decimal point in decimal fractions.

  • When the unit of measure is spelled out, use the singular form when the number is 1. Use the plural form for all other measurements.
    Examples
    0 points
    0.5 points
    1 point
    12 points

  • Spell out by in dimensions, except for tile sizes, screen resolutions, and paper sizes. For those, use the multiplication sign (×). Use a space before and after the multiplication sign.
    Examples
    10 by 12 ft room
    3" by 5" image
    4 × 4 tile
    8.5" × 11" paper
    1280 × 1024

See also Bits and bytes term collection, Numbers

Category Term Abbreviation and usage
Distance and length centimeters cm
feet ft
inches in. (or " if space is limited). Always include a period to avoid confusion with the preposition in.

Hyphenate half-inch as an adjective. Use instead of half an inch or one-half inch.

When space is limited or the measurement needs to be specific, use 0.5 in.

Use the abbreviated form sparingly in content that will be translated or localized. It may be translated incorrectly as a preposition.
kilometers km
meters m
miles mi
millimeters mm
Weight grams g
kilograms kg
ounces oz
pounds lb
Type and fonts points pt
UI, display resolution, and digital imaging pixels Don’t use the abbreviation px in the context of screen or camera resolution.

It’s OK to abbreviate as px in content about online design when space is limited.

Examples
48 × 48 px
The application icon should be 62 × 62 pixels and PNG format.
pixels per inch It’s OK to use the acronym PPI in content about creating digital applications, when space is limited, and when you’re certain that readers will understand it.

Examples
72 pixels per inch
At 72 PPI, ….
megapixels MP
Print and display resolution dots per inch It’s OK to use the acronym dpi to refer to print and display resolution when you’re certain that readers will understand it.
Speed and frequency baud Don't abbreviate. Don't use baud rate—it's redundant. When designating baud, use commas when the number has five (not four) or more digits.

Examples
2400 baud
In 1991, 14.4 K modem had a 2400 baud.
gigahertz GHz. Spell out on the first mention. After that, it’s OK to use the abbreviation as a measurement with numerals.
Hertz Hz. Spell out on the first mention. After that, it’s OK to use the abbreviation as a measurement with numerals. Capitalize the word and the abbreviation.
kilohertz KHz. Spell out on the first mention. After that, it’s OK to use the abbreviation as a measurement with numerals.
megahertz MHz. Spell out on the first mention. After that, it’s OK to use the abbreviation as a measurement with numerals.
Other degrees ° (for temperature)
deg (for angle)
dialog units Don’t abbreviate.

Example
Converting from MFC dialog units (used in resource files to specify height/width) to pixels ….