Measurements and numbers


For nontechnical writing, units of measure should be spelled out.

  • Use a 20-gallon container.
  • The booth will have a 12-foot high wall.
  • Three feet is the same as 36 inches.

Abbreviate units of measure when they occur frequently; in technical work, on invoices, and in tables, for example.  

Units of measure are commonly abbreviated without periods and are the same whether the use is singular or plural:

  • in (inch, inches)
  • yd (yard, yards)
  • ft (foot, feet)
  • mi (mile, miles)
  • mm (millimeter, millimeters)
  • m (meter, meters)

  • km (kilometer, kilometers)
  • A (amp, amps)
  • W (watt, watts)
  • V (volt, volts)

Avoid using symbols (apostrophes and quote marks) to indicate feet and inches.  Instead, for clarity and consistency, use the common abbreviations shown above.  

If there is a possibility of your abbreviation for inch being misread as the preposition (in), abbreviate using a period: in.  

Put a space between the number and the measurement.

  • 5 mm, 250 GHz

Two exceptions do not require a space between the numeral and measurement:

  • Temperature data in a table (40˚C)
  • Gravity (5g - because 5 g would indicate 5 grams)
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In body copy, write out degrees Celsius or degrees Fahrenheit. In charts, the degree symbol ( ˚ ) followed by a C or an F is acceptable.

  • 64 degrees Celsius, 58 degrees Fahrenheit

Not all software programs will covert/recognize a ° symbol, causing confusion in general text.  For that reason, it is best to spell the word in copy and use the symbol for charts/tables.

When using the symbol to express a temperature, include no spaces: 14°C or 14°F.

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Numbers, numerals

Spell out any numbers under 10 (one, two, three, etc.) when they appear in body copy; for 10 and above, use figures (10, 21, 39, etc.).

If a numeral is at the beginning of a sentence, spell it out, or reword the sentence so the numeral is not first.

  • Yesterday, 257 cyclists participated in the race.

For whole numbers in the millions and higher, combine the numeral with the amount: 12 million, 7 billion, 14 ½ million, 3.4 trillion.  A number such as 2, 487,322 should be written in figures.

Use the full spelling of words like first, second, third.  Not 1st, 2nd, 3rd, etc.

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10 a.m.10am, 10 am, 10AM, 10 AM, 10:00
5:30 p.m.5:30pm, 5:30 pm, 5:30PM, 5:30 PM, 5:30
Noon12 p.m., 12pm, 12 pm, 12PM, 12AM, 12:00
Midnight12 a.m., 12am, 12 am, 12PM, 12AM, 12:00

Be aware of your audience.  The U.S. still uses the 12 hour system of telling time.  If your document is intended for a wider audience, however, you may want to choose the 24 hour system, sometimes referred to as Military Style.  

  • 4:00 a.m. (12 hour clock)
  • 0400 (24 hour clock)
  • 3:00 p.m. (12 hour clock)
  • 1500 (24 hour clock)

Using the 24 hour clock, a time like 4:30 a.m. would convert to 0430. (Add zeros to express hours, minutes as two digits.)

Note: Designating a time with a.m. or p.m. is unnecessary when using the 24 hour clock.

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Phoenix Contact has standardized on the international date format (year-month-day) for use in international documents. Exceptions are permitted for “normal” correspondence within a specific country.

If you are creating a technical or other document intended for international use, please use the international date format.

The overriding style of expressing complete dates is the U.S. sequence: month-day-year (October 24, 2014).

However, you must know your audience.  If your document is being prepared for an audience that is accustomed to the International format, then you should use that style.

  • U.S sequence: MM-DD-YYYY (09-01-2014)
  • International sequence: YYYY-MM-DD (2014-01-09)
October 7, 2014

Oct. 7, 2014

October 7th, 2014

When month and date are used, abbreviate Jan.,
Feb., Aug., Sept., Oct., Nov., and Dec. Spell out all
other months.
October 2014Oct. 2014When just month or month and year are used in
body copy, spell out all months.
1990s, 1970s1990’s, 1970’sno apostrophe.
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±No space between ± symbol and value.
/No spaces around the slash mark.  For example: IP65/67, not IP65 / 67
<, >, +, –No space between symbol and unit unless within an equation. Within equations, spaces separate all operators.
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