Number ranges

Express a number range using an unspaced en dash or with words (usually from and to, or between and and):

the dose lasted 2–5 days     the dose lasted from 2 to 5 days

attended the conference on 3–5 May     attended the conference from 3 to 5 May

in the next 10–20 years     in the next 10 to 20 years

the reviewer spent 5–10 hours     the reviewer spent between 5 and 10 hours

When using an en dash to show a range of numbers with unit symbols, the symbol is needed only after the second number:

20–25 km     3–5 m2     1–5 °C     20–30%

Caution! Do not use from or between when expressing a range with an en dash.

If using words to express a range of numbers with unit symbols, the symbol is needed only after the second number (although it can be used after both numbers):

20 to 25 km   or   20 km to 25 km

3 to 5 m2   or   3 m2 to 5 m2

1 to 5 °C   or   1 °C to 5 °C

except if the symbol is closed up to the number:

20% to 30%   not   20 to 30%

If a range starts a sentence, write out the first number and express the second using a numeral, or (preferably) rewrite the sentence:

Nine to 15 L was extracted.   or   We extracted 9–15 L.

Ten per cent to 15 per cent of the 300 people tested ...   or   Of the 300 people tested, 10–15% …

Be careful when using words such as increase by (or from), decrease by (or from) and change by (or from) before 2 numbers in a sentence:

Diameter increased from 2 to 5 cm. [Is this an increase of 2–5 cm or of 3 cm?]

Diameter increased by 2 cm to 5 cm. [Is this an increase of 2–5 cm or of 2 cm?]

The sentence may need to be clarified:

Diameter increased 2–5 cm.
or
Diameter increased by a range of 2 to 5 cm.      
or     
Diameter increased from an initial value of 2 cm to a final value of 5 cm.

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