Quick answer: The correct spelling is forty. The spelling “fourty” is a common misspelling and is never correct in modern English, regardless of whether you are writing in American or British English.
It is one of the most frequent spelling traps in the English language. Because the base number is spelled “four,” our brains naturally want to carry that “u” over into the multiples. However, when you multiply that base by ten, the “u” mysteriously vanishes. As a veteran copy editor who has corrected this exact mistake in thousands of manuscripts, cover letters, and published articles, I can tell you that mastering this single exception will instantly improve the professionalism of your writing.
| Term | Meaning / When to use | Example sentence |
|---|---|---|
| Forty | The correct, standardized spelling of the number 40. Use this in all formal, informal, and professional writing contexts. | She has been working at the company for forty years. |
| Fourty | An incorrect, outdated misspelling of the number 40. Never use this in modern writing, as it is universally considered an error. | (Incorrect) He waited in the lobby for fourty minutes. |
When to use forty
You must use “forty” every single time you need to write out the number 40. This rule is absolute and applies to all contexts, including formal essays, business emails, creative writing, and casual text messages. According to Merriam-Webster, the only widely accepted spelling of the number is “forty,” and this has been the standardized convention since the 16th century.
To demonstrate how this looks in real-world writing, consider these concrete examples where I have frequently seen writers stumble, along with the necessary corrections:
- Professional Email:
- Incorrect: “I will need fourty hours to complete the quarterly audit and submit the final report.”
- Correct: “I will need forty hours to complete the quarterly audit and submit the final report.”
- Resume or Cover Letter:
- Incorrect: “Managed a team of fourty customer service representatives across three regional offices.”
- Correct: “Managed a team of forty customer service representatives across three regional offices.”
- Casual Text Message:
- Incorrect: “Running late, traffic is bad, be there in fourty mins!”
- Correct: “Running late, traffic is bad, be there in forty mins!”
Notice that the correction is always the same: drop the “u.” There is no scenario in modern English where “forty” is considered incorrect, making it a safe, reliable choice for any writer. Furthermore, “forty” can act as an adjective modifying a noun (“forty dollars”), a pronoun standing in for a noun (“I have forty”), or a noun itself (“the roaring forties”). In every single grammatical role, the spelling remains identical.
When to use fourty
The short, definitive answer is that you should never use “fourty.” It is not an acceptable alternative spelling, it is not a regional variation, and it is not a stylistic choice. It is simply a misspelling.
However, understanding why people make this mistake is crucial for avoiding it. The error stems from a cognitive linguistic phenomenon called morphological overgeneralization, or pattern matching. We know that the base number 4 is spelled “four.” We know that 14 is “fourteen.” We know that the ordinal number is “fourth.” Our brains logically assume that 40 should follow the exact same orthographic pattern and retain the “u” as an essential, permanent component of the root morpheme.
I see this error constantly in draft manuscripts, particularly from fast typists who rely on muscle memory rather than visual verification. Writers are so accustomed to typing “four” that their fingers automatically insert the “u” before their conscious mind can stop it. Consider these realistic examples of the error in action and how to fix them:
- Event Invitation:
- Incorrect: “We are celebrating her fourty-fifth birthday next weekend with a large family gathering.”
- Correct: “We are celebrating her forty-fifth birthday next weekend with a large family gathering.”
- Financial Document:
- Incorrect: “The total invoice amount comes to fourty thousand dollars, payable within thirty days.”
- Correct: “The total invoice amount comes to forty thousand dollars, payable within thirty days.”
- Academic Paper:
- Incorrect: “The clinical study observed fourty participants over a six-month period to track the results.”
- Correct: “The clinical study observed forty participants over a six-month period to track the results.”
As Grammarly points out, while “fourty” might have been an accepted variant in Middle English, it is firmly considered a mistake in contemporary usage. If you see “fourty” in your own writing, treat it as a red flag and delete the “u” immediately.
How to remember the difference
If you find yourself second-guessing this spelling, you need a reliable cognitive hook. Relying on “it just looks right” is not enough when your brain is actively trying to trick you with the “four/fourteen” pattern. Here are three editor-approved memory tricks to ensure you never misspell this number again:
- The “U” Drop Mnemonic: Think of the number 40 as being so heavy that it literally drops the “u” from “four.” When you go from four to forty, the “u” falls out of the word entirely.
- The “Fort” Association: The word “forty” contains the word “fort.” A fort is a strong, solid, defensive structure. You can remember that the spelling of 40 is solid and unbreakable, just like a fort, and it does not need the extra baggage or weakness of a “u.”
- The Ordinal Number Trick: This is my favorite editor-level insight. Look at the ordinal numbers. The ordinal for 4 is “fourth” (keeps the u). The ordinal for 40 is “fortieth” (drops the u). If you can remember that “fortieth” has no “u,” you can work backward to remember that the root word “forty” also has no “u.”
Practice writing the word “forty” five times in a row right now. Muscle memory is a powerful tool, and overwriting your old, incorrect habit with the correct spelling will pay dividends in every document you produce.
Common mistakes and exceptions
While the core rule is simple, there are related edge cases and stylistic nuances that trip up even experienced writers.
First, let us address the most persistent myth: the idea that “fourty” is the correct British English spelling and “forty” is the American English spelling. This is entirely false. Both American and British English style guides mandate “forty.” The Oxford English Dictionary and major UK publications strictly use “forty.” If you are writing for a UK audience, you still drop the “u.”
Second, compound numbers can cause hesitation. When writing numbers between 41 and 49, you must use a hyphen, but the base word remains “forty.”
- Correct: forty-one, forty-two, forty-five, forty-nine.
- Incorrect: fourty-one, fourty-five.
Third, historical and cultural terms solidify the “no u” rule. Consider the term “forty-niners,” referring to the prospectors who flocked to California in 1849. It is never spelled “fourty-niners.” Similarly, the phrase “forty winks” (meaning a short nap) has been standardized without a “u” since the early 19th century. Other fixed idioms like “forty days and forty nights” or “forty acres and a mule” further cement this spelling in the cultural lexicon.
Fourth, in the sport of tennis, the score “40” is uniquely called “forty” (widely believed to be a historical shortening of “forty-five”). You will never hear a tennis umpire or see a professional scoreboard that references “fourty.” This sporting idiom alone has reinforced the “no u” spelling for millions of people globally for over a century.
Finally, consider style guide rules regarding when to spell out numbers versus using numerals. The Associated Press (AP) Stylebook dictates that you should spell out numbers one through nine, and use numerals for 10 and above (e.g., “40”). However, the Chicago Manual of Style (CMOS) recommends spelling out numbers from zero to one hundred (e.g., “forty”). Regardless of which style guide you follow, if you are required to spell out the number, it is always “forty.” The stylistic choice is about whether to spell it, not how to spell it.
Frequently Asked Questions
Is “fourty” ever correct in any English dialect? No. “Fourty” is considered a misspelling in all modern dialects of English, including American, British, Canadian, and Australian English.
Why is it spelled “forty” when the number 4 is “four”? The spelling evolved over centuries. In Old and Middle English, the word had many variations, including “fourty.” However, by the 16th century, the “u” was dropped, and “forty” became the standardized, accepted spelling, while “fourteen” retained its “u.”
How do you spell the ordinal number for 40? The correct spelling for the ordinal number is “fortieth.” Just like the base number, it does not contain a “u.”
Should I write “40” or “forty” in formal writing? This depends on your chosen style guide. AP Style prefers the numeral “40,” while Chicago Style prefers spelling it out as “forty.” Always check your specific style guide, but know that if you spell it out, it must be “forty.”
Kimberly Sanchez holds a Bachelor’s degree in Linguistics from UCLA and has spent over a decade working as a language consultant and educator. Her journey in the world of words began with a curiosity about how language shapes our perception of the world. With a keen eye for detail and a knack for making complex concepts accessible, Kimberly specializes in the nuances of English word comparisons and their real-world implications. She joined WordCompareHub to share her insights on frequently confused words and to promote a deeper understanding of language accuracy. Kimberly writes content that is both enlightening and practical, aimed at readers who seek to enhance their communication skills. Outside of her professional pursuits, she is an avid reader and enjoys exploring multilingual environments to observe linguistic diversity in action.