Style Guide > 1 Formatting > [1.101] Measurements
[1.101] Measurements
When you use measurements, follow these conventions:
1.101 Use numerals for all measurements
Use numerals for all measurements, even if the number is under 10. This is true regardless of whether the measurement unit is spelled out or abbreviated. Measurements include distance, temperature, volume, size, mass, pressure, energy, power, bytes, picas, and such, but generally not units of time.
5 centimetres
0.5 cm
8 kPa
three years
3 gigabytes
7 m
1.102 Repeat the unit
For two or more quantities, repeat the unit of measure.
5-metre or 6.5-metre wide road
5 metre and 100 metre
5- or 6.5-metre wide road
5 and 100 metre
Also see Dimensions and Ranges.
1.103 Hyphenating number and unit
Hyphenate a number and its unit of measure when it is preceded by another number. In such cases, spell out one of the numbers. Also hyphenate a number and unit when the combined phrase is used as an adjective. Do not hyphenate if it contains an SI symbol—spell out the unit if necessary. Spelled-out compound adjectives containing non-SI measurements are, otherwise, usually hyphenated.
24 one-kilogram weights, a 1-kilogram weight, a 1 kg weight
twenty-five 150-tonne trucks
two-year outlook, 100-year forecast
five-page report, 50-page report
one-quarter-of-an-inch tolerance, a tolerance of 0.25 inches
12-point type
10-kilometre radius or 10 km radius
50-metre grid or 50 m grid
256 kB RAM
1.104 Dimensions
In most general text, spell out by. The multiplication symbol (ANSI code 0180) is acceptable in informal communications and technical documents. Generally show the unit of measure with each dimension, with the exception of some widely used phrases, such as four-by-two.
42 cm × 23 cm
4.5 m wide by 3.7 m high
8.5-by-11-inch paper
100-metre-by-200-metre grid
an area of 8.5 kilometres by 3 kilometres
1.105 Ranges
In general, use a spaced En dash – or spell out to show ranges of measurements. Generally show the unit of measure with each value. Only use an (unspaced) en dash when the unit of measure is the same for each value and the unit is spelled out.
50 cm – 75 cm
50–75 centimetres
250 kPa – 25 MPa
between 250 kPa and 25 MPa
10% – 12%
10–12 percent
from 10 through 12 percent
85–120 tonnes
85 to 120 tonnes
1.106 SI symbols
The shortened form of an SI unit of measure is known as a symbol, and obeys different punctuation rules to abbreviations. Non-SI units use abbreviations but, for consistency, should be treated as symbols. There are many exceptions and should be studied carefully. For more information, see Symbols.
1 metre, 1 m
5 tonnes, 5 t
0.5 centimetre, 0.5 cm
0 inches, 0 in.
38 percent, 38%
15° 45
′ 10″
38.6 degrees Celsius, 38.6 °C
1.107 Spelling out units of measure
If the symbol is well known (°C, %, m, and kg, for example), it can be used without definition (see Units of measure, common symbols). Always use the spelled out form when discussing units of measure—“The results are shown in megawatt hours (MW·h)”. In general, it’s okay to use symbols when stating a measurement (“The pipeline has a capacity of 35 TJ/d”) and if you have space constraints, in a table for instance. But do define your symbols at first use and in the list of abbreviations in the front matter.
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