Numbers in English seem simple — and in many ways they are — but learners frequently make predictable mistakes that native speakers notice immediately. This guide covers cardinal numbers (one, two, three), ordinal numbers (first, second, third), and the special forms English uses for dates, fractions, percentages, large numbers and mathematical expressions. By the end, you will be able to say and write any number correctly in any context.

Key Takeaways

  • Cardinal numbers count quantity (one, two, three); ordinal numbers express rank or position (first, second, third) and are formed by adding -th to most cardinals, with irregular exceptions for first, second, third, fifth, ninth and twelfth.
  • Compound numbers from 21 to 99 are always hyphenated when written as words: twenty-one, forty-five, ninety-nine.
  • British English uses and after hundreds: one hundred and twenty-three. American English often omits it. British English also writes per cent as two words and reads zero as nought.
  • Dates in British English follow the order day + month + year: 9 June 2026. Always write the month as a word in international communication to avoid confusion with American month/day/year order.
  • One billion means 1,000,000,000 (10⁹) in both British and American English today. Decimals are read digit by digit after the point: 3.14 = three point one four.

Cardinal Numbers (Basic Counting)

Cardinal numbers are the basic counting numbers: one, two, three… The main patterns to learn:

  • 1–20 are individual words you must memorise: one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty.
  • 21–99 follow the pattern tens + ones with a hyphen: twenty-one, thirty-five, forty-eight, sixty-seven, ninety-nine.
  • 100 is one hundred (not a hundred in formal writing, though both are spoken).
  • 100–999: one hundred and twenty-three (British English uses and; American English often omits it: one hundred twenty-three).
  • Thousands: one thousand, three hundred and forty-five. For 1,001–1,099 British English says one thousand and one, one thousand and ninety-nine.
  • Millions and billions: two million, four hundred thousand. Note: one billion = 1,000,000,000 in both British and American English today.

Common mistakes: saying twenty one without a hyphen, or a hundred and one as hundred and one (omitting the article). Always include the hyphen in compound numbers and always include the article before hundred, thousand and million when the number stands alone.

Ordinal Numbers

Ordinals express rank or position: first (1st), second (2nd), third (3rd), fourth (4th)… twentieth (20th). The rules:

  • Irregular forms: first, second, third. These must be memorised — never say oneth, twoth or threeth.
  • Regular -th endings: fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth… Note the spelling changes: five → fifth (not fiveth); nine → ninth (not nineth); twelve → twelfth (not twelwth).
  • Tens ending in -y: change -y to -ieth: twenty → twentieth, thirty → thirtieth, forty → fortieth, fifty → fiftieth.
  • Compound ordinals: only the final word takes the ordinal ending: twenty-first (21st), forty-third (43rd), one hundredth (100th), one thousand and first (1,001st).

Ordinals are used for dates (the ninth of June), positions in a sequence (the second chapter, the third floor), fractions (two thirds, four fifths), and rankings (first place, third prize).

Dates in British English

British English writes dates as day + month + year: 9 June 2026, or 9th June 2026. Spoken: the ninth of June two thousand and twenty-six. In numerical format: 09/06/2026 (day/month/year).

American English reverses this order: June 9, 2026, spoken as June ninth, twenty twenty-six. The numerical American format is 06/09/2026. This difference causes real confusion in international communication — the same string of digits means different dates in each country. The safe solution is always to write the month as a word: 9 June 2026 is unambiguous anywhere in the world.

For years: 1945 = nineteen forty-five; 2000 = two thousand; 2008 = two thousand and eight; 2026 = twenty twenty-six.

Fractions

Simple fractions use a cardinal number for the top (numerator) and an ordinal for the bottom (denominator):

  • ½ = a half / one half (not one second)
  • ⅓ = a third / one third
  • ¼ = a quarter / one quarter (more natural than one fourth in British English)
  • ¾ = three quarters
  • ⅖ = two fifths; ⅜ = three eighths

Plural denominators: when the numerator is two or more, the denominator takes a plural -s: two thirds, three fifths, seven eighths. Mixed numbers are written with and: 1½ = one and a half; 2¾ = two and three quarters.

Decimals and Percentages

Read decimals digit by digit after the decimal point, introduced by the word point:

  • 3.14 = three point one four (never three point fourteen)
  • 0.5 = nought point five (British English) or zero point five (American English)
  • 25.75 = twenty-five point seven five
  • 100.01 = one hundred point zero one

For percentages: 25% = twenty-five per cent (British English, two words) or twenty-five percent (American English, one word). 7.5% = seven point five per cent. In formal British writing, always use the two-word form per cent.

Large Numbers

The key milestones to know:

  • 1,000 = one thousand
  • 10,000 = ten thousand
  • 100,000 = one hundred thousand
  • 1,000,000 = one million
  • 1,000,000,000 = one billion
  • 1,000,000,000,000 = one trillion

Common mistakes: saying one thousand million instead of one billion (technically correct but old-fashioned in modern British English); using k in formal writing (£50k is acceptable in informal business writing only). When reading out longer numbers such as 1,250,000, say: one million two hundred and fifty thousand — work from left to right, largest unit first.

Mathematical Expressions

English has specific vocabulary for reading mathematical operations aloud:

  • + = plus / and: 5 + 3 = five plus three equals eight
  • − = minus / take away: 10 − 4 = ten minus four is six
  • × = times / multiplied by: 6 × 7 = six times seven equals forty-two
  • ÷ = divided by: 12 ÷ 4 = twelve divided by four is three
  • = = equals / is
  • 2² = two squared; 3³ = three cubed; 2⁴ = two to the power of four
  • √16 = the square root of sixteen

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Frequently Asked Questions

How do you write numbers as words in English?
Numbers 1–9 are always written as words in formal writing (one, two, three). Numbers 10 and above are typically written as figures (10, 25, 100) unless they start a sentence. Compound numbers from 21–99 are hyphenated when written as words: twenty-one, forty-five. Large round numbers are often written as words for emphasis: a million possibilities.
What is the difference between cardinal and ordinal numbers?
Cardinal numbers count quantity: one, two, three, four. Ordinal numbers express position or rank: first, second, third, fourth. Cardinals answer “how many?” Ordinals answer “which one in a sequence?” Use ordinals for dates (the fifth of June), rankings (third place), and sequences (the second chapter).
How do you say years in English?
Years 1100–1999: say as two two-digit numbers — 1945 = nineteen forty-five, 1066 = ten sixty-six. Years 2000–2009: two thousand, two thousand and one, two thousand and nine. Years 2010 onwards: say as two two-digit numbers — 2024 = twenty twenty-four, 2026 = twenty twenty-six. Exception: 2000 = two thousand, 2001–2009 = two thousand and one to two thousand and nine.
How do you write the date in British English?
The British order is day + month + year: 9 June 2026 (no comma). Spoken: the ninth of June two thousand and twenty-six. In numerical format: 09/06/2026 (day/month/year). Note: in American English the order is month/day/year, so 09/06/2026 would be read as September 6th — always write the month as a word in international communication.
What is the difference between a billion in British and American English?
Historically, British English used “billion” to mean one million million (10¹²), while American English used it to mean one thousand million (10⁹). Today, British English has adopted the American meaning. One billion = 1,000,000,000 (10⁹) in both varieties. The old British “billion” is now obsolete in everyday usage.
How do you say fractions in English?
Use a cardinal number for the top (numerator) and an ordinal for the bottom (denominator): one third (1/3), two fifths (2/5), three eighths (3/8). Exceptions: one half (not one second) and one quarter / three quarters (more common than one fourth / three fourths). Mixed numbers: three and a half, two and three quarters.
How do you read decimal numbers in English?
Say the whole number, then “point”, then each digit separately: 3.14 = three point one four. 0.5 = zero point five (AmE) or nought point five (BrE). 25.75 = twenty-five point seven five. Do not say “point seventy-five” — read each digit: point seven five.
When do you use a hyphen in number words?
Hyphenate compound numbers between 21 and 99 when written as words: twenty-one, forty-five, ninety-nine. Do not hyphenate “one hundred”, “one thousand”, “one million”. Do hyphenate when used as compound adjectives before a noun: a twenty-four-hour period, a three-hundred-page book.
What is the correct way to say telephone numbers in English?
British English reads phone numbers as individual digits: 020 7946 0958 = oh-two-oh, seven-nine-four-six, oh-nine-five-eight (where “oh” = zero). American English also reads individual digits but uses “zero” more consistently. Doubles are sometimes said together: 44 = double four. 0800 numbers: oh-eight-hundred.
How do you say large numbers like millions in English?
Say the number in millions/billions with any remaining part after: 1,250,000 = one million two hundred and fifty thousand. 3,500,000,000 = three billion five hundred million. In informal contexts, “3.5 billion” is acceptable: three point five billion. For very large technical numbers, scientific notation is used: 3.5 × 10⁹.