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NIST standards are widely used in scientific and technical communities, providing a consistent and reliable framework for communicating and interpreting numerical information. By following these standards, we can better communicate numerical values to our audience, who may be more accustomed to seeing this style (as opposed to the AP or Chicago styles used for marketing content).

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Units of Measurement

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US Customary Units

Length:
  • Inch: in
  • Foot: ft
  • Yard: yd
  • Mile: mi
  • Mils: mil
  • Gauge: ga
Mass:
  • Ounce: oz
  • Pound: lb Note: The abbreviation for “pound” is “lb,” not “lbs”.
Volume:
  • Fluid ounce: fl oz
  • Cup: c
  • Pint: pt
  • Quart: qt
  • Gallon: gal
Temperature:
  • Degree Fahrenheit: °F
Force:
  • Pound-force: lbf
Pressure:
  • Pounds per square inch: psi
Energy:
  • British Thermal Unit: BTU

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SI Units

Length:
  • Millimeter: mm
  • Centimeter: cm
  • Meter: m
  • Kilometer: km
Mass:
  • Milligram: mg
  • Gram: g
  • Kilogram: kg
  • Tonne: t
Volume:
  • Milliliter: mL
  • Liter: L
Temperature:
  • Degree Celsius: °C
  • Kelvin: K
Time:
  • Second: s
  • Minute: min
  • Hour: h
  • Day: d
Force:
  • Newton: N
Pressure:
  • Pascal: Pa
  • Kilopascal: kPa
  • Megapascal: MPa
  • Bar: bar
Energy:
  • Joule: J
  • Calorie: cal
  • Kilowatt-hour: kWh

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Computing

Data Storage and Memory:
  • Byte: B
  • Kilobyte: KB
  • Megabyte: MB
  • Gigabyte: GB
Data Transfer Rates:
  • Bits per second: bps
  • Kilobits per second: Kbps
  • Megabits per second: Mbps
  • Gigabits per second: Gbps
Processing Power:
  • Hertz: Hz
  • Megahertz: MHz
  • Gigahertz: GHz

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US Customary Units vs. SI Units

In the United States, both US Customary Units and SI Units are used. Determine usage based on context: US Customary Units
  • Standard Material Sizes: For lumber, drywall, piping, and materials sold in inches/feet/yards. Example: “Cut the 2x4 lumber to 8 feet.”
  • Tools and Equipment: For measurements taken with tape measures, rulers, or framing squares. Example: “Mark the plywood every 16 inches for stud placement.”
  • Industry-Specific Standards: If the standard or code is in US Customary Units. Example: “Ensure a minimum clearance of 36 inches around electrical panels.”
SI Units
  • Engineering Calculations and Scientific Data: For stress analysis, fluid dynamics, and similar technical applications. Example: “The stress on the beam is 24.5 MPa.”

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Decimals vs. Fractions

Use decimals or fractions according to the context of the measurement: Decimals
  • Engineering/Scientific Data: Decimals ensure precision. Example: “The stress on the beam is 3.56 kPa.”
  • Currency and Financial Values: Example: “The total cost of the project is $12,345.67.”
  • Percentages and Ratios: Example: “The mixture consists of 75.5% sand and 24.5% cement.”
Fractions
  • Dimensions, Measurements, and Construction: Fractions align with industry standards. Example: “The stud needs to be cut to 7 1/4 inches.”
  • Standard Material Sizes: Example: “Use a 2x4 lumber piece for framing.”
  • Tools and Equipment: Fractional units match tool markings. Example: “Mark the plywood at 3 3/8 inches from the edge.”

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Guidelines

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1. Decimal Format

Do

2 in 0.2

Don't

2 in. (with a period) .2 (no leading zero)

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2. Fraction Format

  • Use reduced fractions and a space between the whole number and fraction.

Do

7 1/4 inches 5/8 inch 8 1/2 feet 4 3/4 yards

Don't

7 2/8 inches (not reduced) 3/6 inch (not reduced) 8-1/2 feet (with a hyphen) 4.3/4 yards (with a period)

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3. Spelling Out Numbers

Do

Twenty-four

Don't

Twenty four
(Use a hyphen for numbers 21–99.)

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4. Ranges

  • Use an en dash (–) for ranges.
  • For percentages, include % on both numbers.
  • For measurements, only put the unit after the second number.

Do

25–75 cm 25%–75%

Don't

25 cm–75 cm 25–75%

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5. Expressing Ranges in Text

  • “Between A and B” includes both endpoints.
  • “From A to B” may not include B.

Do

“Enter a number between 1 and 10.” “Customer Service is open from 9 AM to 5 PM.”

Don't

“Enter a number from 1 to 10.” “Customer Service is open between 9 AM and 5 PM.”

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6. Large Numbers

Use commas for the thousands separator.

Do

1,000,023

Don't

1000023

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7. Consistency

Maintain the same unit and precision within a section.

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8. Symbols and Abbreviations

Use symbols for inches and feet if space is limited, otherwise use abbreviations.

Do

5 ft 10 in

Don't

5’ 10”

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9. Temperature

  • Use the degree symbol (°) without space before F or C.
  • Place minus signs directly before negative values.
  • Round appropriately.

Do

75°F (24°C)

Don't

5 °F (24 °C) (spacing issues)
75 F (24 C) (missing degree symbol)

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References

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