0 zero    
1 one first 1st
2 two second 2nd
3 three third 3rd
4 four fourth 4th
5 five fifth 5th
6 six sixth 6th
7 seven seventh 7th
8 eight eighth 8th
9 nine ninth 9th
10 ten tenth 10th
11 eleven eleventh 11th
12 twelve twelfth 12th
13 thirteen thirteenth 13th
14 fourteen fourteenth 14th
15 fifteen fifteenth 15th
16 sixteen sixteenth 16th
17 seventeen seventeenth 17th
18 eighteen eighteenth 18th
19 nineteen nineteenth 19th
20 twenty twentieth 20th
21 twenty-one twenty-first 21st
22 twenty-two twenty-second 22nd
23 twenty-three twenty-third 23rd
24 twenty-four twenty-fourth 24th
25 twenty-five twenty-fifth 25th
26 twenty-six twenty-sixth 26th
27 twenty-seven twenty-seventh 27th
28 twenty-eight twenty-eighth 28th
29 twenty-nine twenty-ninth 29th
30 thirty thirtieth 30th
40 forty fortieth 40th
50 fifty fiftieth 50th
60 sixty sixtieth 60th
70 seventy seventieth 70th
80 eighty eightieth 80th
90 ninety ninetieth 90th
100 one hundred hundredth 100th
1000 one thousand thousandth 1000th
1 000 000 one million millionth 1 000 000th
1 000 000 000 one billion billionth 1 000 000 000th

Words or figures?

A common rule for writing numbers is to write one, two, three, four, five, six, seven, eight, nine and ten as words, but larger numbers as figures.

The following numbers may also be written as words in normal text:

twenty sixty hundred
thirty seventy thousand
forty eighty million
fifty ninety billion

Approximate versus exact

Compare also the examples below where words are used for approximate amounts and figures for exact values:

There have been over fifty new cases this year.
There have been 54 new cases this year.

There are around five thousand new students every year.
Last year there were 5023 new students.

Use figures with units or abbreviations

3% 10 kg
6 mm 100 km
25 °C pH 7

Use figures with page, figure and table numbers

page 1 p. 100
Figure 6 Fig. 8
Table 3  

Use figures with dates

19 February 2014
October 11, 2015

Avoid beginning a sentence with a figure

In university and research writing you should avoid beginning a sentence with a figure, for example:

1 in 10 pregnancies …
Better: One in ten pregnancies …

2.5 mg of distilled water were added after 30 minutes …
Better: After 30 minutes, 2.5 mg of distilled water were added …

50% of students at some UK universities come from private schools …
Better: Fifty percent of students at some UK universities come from private schools …

Avoid mixing words and figures

Where possible, avoid mixing words and figures in the same sentence, particularly when comparing. For example:

Compulsory education in Britain is from five to 16, though many children begin preschool at 3 or four.

Better: Compulsory education in Britain is from 5 to 16, though many children begin preschool at 3 or 4.

Avoiding ambiguity

However, where necessary numbers should be written as words or figures to avoid ambiguity, for example:

three 5-point scales
five 10-year-old children

Values over a million

Some values over a million, particularly currencies, may be written as a combination of figures and words, particularly when round figures:

£3 million
USD 10 billion

Similarly with populations:

The population of the UK is around 60 million.


In English, do not add –s to specific multiples of a hundred, thousand, million or billion. For example:

two hundred (not two hundreds)
three thousand (not three thousands)
four million (not four millions)
five billion (not five billions)

However, an -s is indeed added to the general multiples hundreds, thousands, millions and billions:

Hundreds of researchers attended this year’s conference.
Thousands of people die of preventable diseases every day.
The cost may run into the millions, even billions.

In British English, when pronouncing numbers over 100 or writing them in words, and is always added before any units under 100:

110 one hundred and ten
125 one hundred and twenty-five
150 one hundred and fifty
175 one hundred and seventy-five


Multiples of a thousand are marked by a space or comma. A common rule in university and research texts is to write numbers under 10 000 without commas or spacing, and numbers 10 000 and over with commas or spacing. Some authors and publishers also divide four-figure numbers, for example 3 987 or 3,987.

Spacing Commas
3987 or 3 987 3987 or 3,987
29 483 29,483
6 728 349 6,728,349

A space is less ambiguous as the comma is used in some countries as the decimal symbol, for instance 3,142. As always, be consistent throughout your text and follow any guidelines for your subject or publication.

Do not use a point to mark thousands

In English, unlike some languages, the point is not used to mark thousands:

3.500 means 3½, not 3500

Do not add commas or spaces in page numbers

page 1234, not page 1 234 or page 1,234


Beware of ambiguity when reading or writing billion in British English:

£5 billion
£10 billion

Although billion is now normally used in British English to mean a thousand million (109) as in US English, it also has an earlier meaning of a million million (1012).


Decimals in English are indicated by a point, not a comma as in some languages. For example:

a half 0.5
a third 0.333
a quarter or fourth 0.25
a fifth 0.2

If you normally use a comma for decimals in your country, be sure to carefully check your figures in English as this is a potential source of major error.


Common, single fractions do not need a hyphen:

½ one half
one third
¼ one quarter or fourth
one eighth

But others generally do:

¾ three-quarters or three-fourths


The British spelling is per cent as two words and the US spelling percent as one word, though this is not a hard-and-fast distinction.

You should be consistent in your text in your use of %, per cent or percent:

ten per cent ten percent
10 per cent 10 percent
10% not ten %

The % symbol should always be written next to its number without a space:

Not: 100 %

Mathematical symbols

Be consistent in the spacing of symbols in your text, for example:

1 + 1 = 2
5 − 3 = 2
< 10
> 6

On your computer, use the minus sign rather than a hyphen (-) or en dash (–), as these can be separated from their number at the end of a line. This is also the case for superscripts. The correct minus sign stays with its number even at the end of a line.


Roman numerals

Roman numerals are sometimes used in university and research writing, for example for the preliminary pages of a book and sometimes for chapter numbers and bullets.

Arabic Numeral Roman Upper Case Roman Lower Case
1 I i
2 II ii
3 III iii
4 IV iv
5 V v
6 VI vi
7 VII vii
8 VIII viii
9 IX ix
10 X x
50 L l
100 C c
500 D d
1000 M m

How to calculate Roman numerals

Add numbers after a symbol of equal or greater value:

XX = X + X = 20
CX = C + X = 110

Subtract numbers before a symbol of greater value:

IX = X – I = 9
XC = C – X = 90

Greek and Latin numerical affixes

Numerical Value Greek or Latin
1 mono, uni
2 di, bi, du
3 tri, ter
4 quadr
5 penta, quin
6 hexa, sex
7 sept, hept
8 oct
9 non, nona
10 dec
11 hendeca
12 dodeca
100 cent
1000 milli, mille


semi, demi, hemi half
haplo single
diplo double
dicho in two
proto first
deuter second
oligo few
pluri several
multi, poly much or many