ANSI Unit Abbreviations

Abbreviations for pressure and many other units help communicate technical information quickly.
Abbreviations for pressure and many other units help communicate technical information quickly. (Image: Billy Gadbury/Hemera/Getty Images)

Abbreviations are short references for long terms. In engineering and technical writing, the wide array of long words has led to a diversity of abbreviations meant to reduce the amount of text required to convey the same ideas. Yet variation in abbreviations can lead to confusion as to what an abbreviation means. The American National Standards Institute adopts its standards on abbreviations for technical terms from the American Society of Mechanical Engineers. ANSI standards are primarily American units. However, ANSI unit abbreviations include metric units, scientific terms and common units of measurement, such as time.

ANSI Abbreviation Standards

ANSI standard Y1.1, “Abbreviations for Scientific and Engineering Terms,” was the original standard for abbreviations for technical terms. Y1.1 was updated in 1989. ANSI standard Y1.1 was replaced by ANSI standard Y14.38 in 1999. ANSI standard Y14.38 was updated in 2007.

Metric Units

Metric units, or International System of Units, are also called SI units. ANSI standards for metric unit abbreviations include “cm” for centimeter, “cc” for cubic centimeter, and “m” for meter. Cubic meter is abbreviated to ”cu m,” while cubic millimeter is “cumm.”

American Units

American units are also called English units, though England has switched to the metric system. ANSI standards for American units include “ft” for feet, “cu ft” for cubic feet, and “mi” for mile. Feet-per-minute is identified as “fpm.”

Universal Units

ANSI standards also provide approved abbreviations for units of time, mathematical terms and commonly used long technical terms. ANSI calls for revolutions per minute to be abbreviated as “rpm ,”while revolutions per second are “reps.” Powerfactor is abbreviated to “pf.” Temperature is abbreviated to “temp.” ANSI also specifies abbreviations for mathematical terms. For example, tangent is abbreviated as “tan,” while second becomes “s” or “sec.” Diameter is abbreviated as “dia.” Coefficient is abbreviated as “coef.” Hour can be shortened to “h” or “hr.”

Drafting Unit Standards

ASME/ANSI standard Y14.5 includes abbreviations to be used in dimensioning and tolerance call-outs on drawings. According to “Engineering Design with SolidWorks 2011,” by David and Marie Planchard, “millimeter (MMGS) dimensioning and decimal inch (IPS) dimensioning are the two most common unit types specified for engineering parts and drawings.” Drawings created to the ANSI standard will have American units first, with metric dimensions listed second.

ANSI also has a standard for abbreviations as they are used on drawings.
ANSI also has a standard for abbreviations as they are used on drawings. (Image: Images)

Abbreviations in Technical Writing

There is no need to include an “s” after a unit abbreviation. According to the “Handbook of Technical Writing” by Gerald Alred, Charles Brusaw, and Walter Oliu, “abbreviations of units of measure are identical in the singular and plural.” When a period is used at the end of an abbreviation as well as at the end of a sentence, a second period is not required. It is recommended, but not required, to include a period after units that could be mistaken for a word, such as “in” for inches.

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