What the style guides say about numbers

When to spell a number out, where the commas go, how to write a date: four free style guides answer the same questions, sometimes the same way and sometimes not. Here they are side by side, in their own words.

The four guides

Each is free to read in full, and each was read on 25 September 2026: the GOV.UK A to Z style guide, written for GOV.UK; the Guardian style guide, the newspaper's own; the Microsoft Style Guide; and the Google developer documentation style guide. Every entry below is quoted word for word. A dash means the part of the guide read for this page does not say, which is not the same as the guide having no view.

Paid-for guides are left out, and none is described from memory.

What four style guides say about writing numbers, quoted
Question	GOV.UK	Guardian	Microsoft	Google
One to nine	“Write all other numbers in numerals (including 2 to 9) except where it’s part of a common expression like ‘one or two of them’ where numerals would look strange.”	“Spell out from one to nine; numerals from 10 to 999,999”	“In body text, spell out whole numbers from zero through nine, and use numerals for 10 or greater.”	“In general, spell out the following: Numbers from zero through nine, except as noted in Numbers as numerals.”
A number that starts a sentence	“If a number starts a sentence, write it out in full (Thirty-four, for example) except where it starts a title or subheading.”	—	“Don't start a sentence with a numeral.”	“A number that starts a sentence. Recommended: Fifteen directories are created.”
Commas in long numbers	“For numerals over 999, insert a comma for clarity: 9,000.”	—	“Use commas in numbers that have four or more digits.”	“in numbers four or more digits long, use commas to set off groups of three digits, counting leftward from the decimal point”
Millions and billions	“Always use million in money (and billion): £138 million.”	“thereafter use m, bn or tn for sums of money, quantities or inanimate objects in copy, eg 5m tonnes of coal, 30bn doses of vaccine, £50tn; but million or billion for people or animals”	“In general, don't abbreviate thousand, million, and billion as K, M, and B.”	“Using words like millions or billions is fine for approximate numbers. For precise numbers, use numerals.”
Percentages	“Use a % sign for percentages: 50%.”	“% in headlines and copy”	“Use a numeral plus percent to specify a percentage.”	“In general, use numerals and the percent sign (%), without a space between them.”
Ordinals	“Spell out first to ninth. After that use 10th, 11th and so on.”	“spell out ordinals from first to ninth, thereafter 10th, 31st, etc”	“Always spell out ordinal numbers.”	“Spell out all ordinal numbers in text.”
Fractions	“Write out and hyphenate fractions: two-thirds, three-quarters.”	“two-thirds, five-eighths, etc, but two and a half, three and three-quarters, etc.”	“Hyphenate spelled-out fractions.”	“Express fractions as decimal numbers, when possible.”
Ranges	“Use ‘500 to 900’ and not ‘500-900’ (except in tables).”	—	“In most cases, use from and through to describe a range of numbers.”	“Use a hyphen with no space on either side of it. Do not use an en dash”
Dates	“do not use a comma between the month and year - for example: 4 June 2017”	“Our style is: 21 July 2016 (day month year; no commas).”	“Use the following format for dates: month day, year, as in July 31, 2016.”	“Recommended: January 19, 2017”
Negative numbers	“Use a minus sign for negative numbers: –6”	—	“Form a negative number with a minus sign, not an en dash”	“In general, use numerals for the following: … Negative numbers.”

Where they agree

The three that address it write a number that starts a sentence in words, or say not to start with a numeral at all: GOV.UK's example is Thirty-four. The three that address long numbers group them with commas. And all four hyphenate a fraction written in words, two-thirds; Google prefers a decimal where one will do, and says that when a fraction must be words, to “connect the numerator and denominator with a hyphen”.

Where they split

One to nine. The Guardian, Microsoft and Google spell them out; GOV.UK writes 2 to 9 as numerals and keeps the word for one and for common expressions.

Millions. The Guardian writes £50tn and 5m tonnes in copy; GOV.UK and Microsoft spell the word out; Google takes the word for an approximate number and numerals for a precise one.

Dates. GOV.UK and the Guardian put the day first, Microsoft and Google the month. Dates and years in words writes any date both ways.

Ordinals. GOV.UK and the Guardian spell out first to ninth and write 10th onwards in figures; Microsoft and Google spell every ordinal out in running text.

Ranges. GOV.UK writes 500 to 900, Microsoft from 9 through 17, and Google a hyphen, 2012-2016.

What the converters do

The converters write numbers in words, so the question of words or figures is yours; what they settle is the spelling once you have chosen words. Compound numbers take a hyphen, as the Microsoft guide also asks: “Hyphenate compound numbers when they're spelled out.” A long number is grouped with commas when it is echoed back. And the British or American “and” is your choice on every tool.