Use the slash (/) in place of ‘per’ between two abbreviated units of measurement.
Use the degree sign (°) with angles, temperatures [except metric K (Kelvin)], and compass coordinates.
Abbreviate units of measurement in the text only when used with numerical values (unless the abbreviation replaces a very long phrase, such as ‘several scf/D’ for ‘several standard cubic feet per day’). 25 ft
50 x 103 ft3/D
Use the same abbreviation for both singular and plural forms of measurements.