Company Writer's Guide
[For Illustration Only] B-4
Symbols for Units in General Use
Unit Symbol Notes
ampere A SI unit of electric current.
ampere (turn) A SI unit of magnetomotive force.
ampere-hour Ah Also A•h
ampere per meter A/m SI unit of magnetic field strength.
angstrom
Δ
1 Δ = 10
-10
m (deprecated, see ANSI Z210.1-1976)
atmosphere, standard atm
1 atm = 101 325 Pa (deprecated, see ANSI Z210.1-
1976)
atmosphere, technical at
1 at = 1 kgf/cm
2
(deprecated,
see ANSI Z210.1-1976)
atomic mass unit (unified) u
The (unified) atomic mass unit is defined as one
twelfth of the mass of an atom of the
12
C nuclide.
Use of the old atomic mass (amu), defined by
reference to oxygen, is deprecated.
atto a SI prefix for 10
-18
.
attoampere aA
bar bar
1 bar = 100 kPa. Use of the bar is strongly
discouraged (see ANSI Z210.1-1976), except for
limited use in meteorology.
barn b 1 b = 10
-28
m
2
barrel bbl 1 bbl = 42 gal
US
= 158.99 L
barrel per day bbl/d
This is the standard barrel used for petroleum,
etc. A different standard barrel is used for fruits,
vegetables, and dry commodities.
baud Bd
In telecommunications, a unit of signaling speed
equal to one element per second. The signaling
speed in bauds is equal to the reciprocal of the
signal element length in seconds.
