Don’t add s to an abbreviated SI unit to form its plural. Abbreviated SI units do not have a separate plural form.
- 1 kg, 2 kg (not 2 kgs)
pronounced as “2 kilograms“
- 500 g (grams)
- 100 m (meters)
- 10 km (kilometers)
- 60 s (seconds)
- 3600 ms (milliseconds)
- 40 A (amperes)
- 273.15 K (kelvins)
Not adding s to an abbreviated unit of measurement helps avoid ambiguity: “10 m” is “10 meters,” while “10 ms” is “10 milliseconds.”
For quantities other than one, even those less than one, the unit is read aloud as plural: one meter (1 m), but zero point five meters (0.5 m), one point five meters (1.5 m), and of course two meters (2 m).
Non-SI units accepted for use with SI units also do not have separate plural forms: no s is added to the abbreviation for the plural, although the unit is read aloud as plural.
- 2 eV (electron volts)
- 10 t (tonnes)
- 100 ha (hectares)
Plurals of abbreviated non-metric units
Abbreviations of non-metric or US units, common in American usage, also do not have separate plural forms: don’t add s to form the plural.
- 3 lb. (pounds)
- 5 sq. yd. (square yards)
- 10 mi. (miles)
- 15 yd. (yards)
- 5 ft. (feet)
- 10 in. (inches)
- 6 oz. (ounces)
- 12 fl. oz. (fluid ounces)
Units of time are an exception.
Plurals of abbreviated units of time
The SI unit of time is the second, abbreviated to “s.” It does not have a separate plural form.
- 1 s, 10 s (not “10 ss” for “10 seconds”)
However, units of time traditionally used in nontechnical, nonacademic writing may take s to form the plural: sec/secs, min/mins, hr/hrs, yr/yrs. A period may also be used to denote the abbreviation.
- Preparation time: 20 mins
Cooking time: 45 mins
Total time: 1 hr 5 mins
- Best lap time: 47 secs
- For children aged 4–11 yrs.
The s is often omitted with min and sec.
- Cook for 4-6 min. until tender.
Some non-SI units (d, h, min for day, hour, minute) are acceptable in technical contexts and compatible for use with the SI unit of time (s for second). When used in academic or technical writing, they do not have a separate plural form—that is, they do not take s to form the plural.
- 4 min 20 s (4 minutes and 20 seconds)
- 8 h (hours)
- 10 d (days)