6Numbers

6.1Numerals

For numerals greater than or equal to one, U.S. English uses commas to separate digits in groups of three.

Simple fractions can be spelled out. These include halves, thirds, and quarters of a whole. For example:

Browsers with Opera Turbo use up to half the amount of data of traditional browsers.

A decimal point is used to indicate complex fractions of a whole, when they are needed. Whole numbers should never appear with a decimal point. For numbers less than one, precede the decimal with a zero. For example:

The newest release shortened launching times by 0.34 seconds.

6.2Numbers in body copy

In general, for non-technical references, spell out single-digit numbers (0-9) and use numerals for all others. Avoid beginning sentences with numerals. For example:

Nokia will ship two new devices with Opera Mini, introducing 150,000 new users to the popular browser.

These rules apply to ordinals, cardinals, and physical quantities:

In 15 minutes, Opera will reveal the first-place winner in our list of top 100 extensions.

Technical references should retain the numerals associated with the industry's common naming practice, including version or model numbers, when needed. For example:

Opera now supports HTML5 video on its 64-bit Linux browser.

When referencing percents, always use a numeral followed by the word "percent":

Opera Mini users saved an average of 81 percent of their mobile data.

Numbers larger than 999,999 (≥ 1 million) should mix numerals with spelled-out numbers, preferring the smallest numeral possible. Avoid fractions. Use a decimal rounded to the nearest tenth of the whole, where needed. For example:

Indian users' savings totaled 2.1 billion in six months, roughly 350 million rupees per month.

6.3Numbers in titles, headlines and subsection headings

In general, numerals are acceptable in titles, headlines, or subsection headings when used sparingly. Percentages benefit from using the "%" sign. For example:

3 ways to extend your data plan by 50%

When referencing decades, use an apostrophe to abbreviate the century. There should be no apostrophe between the year and the "s". For example:

Flashback: Check out how Opera looked in the '90s