Have you ever stopped while writing a date or birthday message and wondered whether to write 13rd or 13th? The confusion is understandable because numbers such as 3rd, 23rd, and 33rd use “rd.” However, 13 follows a special rule.
The correct form is 13th, while 13rd is incorrect.
In this guide, you will learn exactly why 13th is correct, how ordinal number suffixes work, where people commonly make mistakes, and how to remember the rule easily.
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13rd vs 13th: The Quick Answer
The answer is simple: 13th is correct, and 13rd is wrong.
The number 13 is an ordinal number when it shows position, order, rank, or a date. Its correct written form is 13th, or thirteenth when written in words.
Correct Usage of 13th
Use 13th when referring to:
- The 13th day of a month
- The 13th position in a competition
- A 13th birthday
- The 13th chapter
- The 13th floor
- The 13th item in a sequence
For example:
- My birthday is on the 13th of May.
- She finished in 13th place.
- Today is his 13th birthday.
- Please read the 13th chapter.
Cambridge Dictionary defines thirteenth as the ordinal form written as 13th, while Merriam-Webster also identifies it as the number 13 in a countable series.
Why 13rd Is Incorrect
The mistake happens because people see the last digit 3 and assume it should use the suffix rd, just like:
- 3rd
- 23rd
- 33rd
- 43rd
However, 13 is an exception. Numbers ending in 11, 12, or 13 use th instead of st, nd, or rd.
Therefore:
- 11th ✔
- 12th ✔
- 13th ✔
- 13rd ✘
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Why 13th Is Correct: The Ordinal Number Rule
To understand 13rd vs 13th, you first need to understand ordinal numbers.
Ordinal numbers show the position of something in an ordered sequence. For example:
- 1st = first
- 2nd = second
- 3rd = third
- 4th = fourth
Merriam-Webster defines an ordinal number as a number that indicates the place of an item in an ordered sequence.
The Basic Ordinal Suffix Rule
In most cases, English ordinal numbers follow this pattern:
| Last Digit | Usual Suffix | Example |
|---|---|---|
| 1 | st | 1st, 21st |
| 2 | nd | 2nd, 22nd |
| 3 | rd | 3rd, 23rd |
| Other digits | th | 4th, 14th, 25th |
This rule is easy to follow until you reach numbers ending in 11, 12, and 13.
The 11, 12, and 13 Exception
Numbers ending in 11, 12, or 13 always use th.
For example:
- 11th, not 11st
- 12th, not 12nd
- 13th, not 13rd
- 111th, not 111st
- 112th, not 112nd
- 113th, not 113rd
This exception is the key to understanding the correct form.
Easy Memory Trick for 13th
Remember this simple phrase:
“11, 12, and 13 always choose TH.”
So, even though 13 ends in the digit 3, you should not look only at the final digit. Check whether the number ends in 11, 12, or 13 first.
13rd vs 13th: Real Examples in Everyday English
The difference becomes even clearer when you see the correct form in real sentences.
Dates
Correct:
- The event will take place on June 13th.
- My appointment is on the 13th of September.
- We arrived on the 13th.
Incorrect:
- The event will take place on June 13rd. ✘
- My appointment is on the 13rd of September. ✘
Rankings and Positions
Correct:
- He finished 13th in the race.
- Our team is currently in 13th place.
- She was the 13th person to arrive.
Incorrect:
- He finished 13rd in the race. ✘
Birthdays and Anniversaries
Correct:
- Happy 13th birthday!
- Today is their 13th wedding anniversary.
- The company is celebrating its 13th year.
Incorrect:
- Happy 13rd birthday! ✘
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13rd vs 13th Case Study: A Simple Real-Life Writing Example
Imagine a student named Adam who is preparing an invitation for his sister’s birthday party. He writes:
“Please join us to celebrate Sara’s 13rd birthday on the 13rd of July.”
At first glance, Adam believes this is correct because he remembers the pattern 3 → 3rd. Since 13 also ends in 3, he assumes the same rule applies.
However, when his teacher reviews the invitation, she corrects both mistakes to:
“Please join us to celebrate Sara’s 13th birthday on the 13th of July.”
The teacher explains that ordinal numbers ending in 11, 12, and 13 follow a special exception. Therefore, Adam should focus on the final two digits, not just the last digit.
This example shows why 13rd vs 13th is a common confusion. The normal rule says numbers ending in 3 often use “rd,” but 13 is part of a special group. Once Adam learns the exception, he can also correctly write 113th, 213th, and 1013th.
The lesson is simple: check the last two digits before choosing an ordinal suffix. This small habit prevents one of the most common ordinal number mistakes.
What the Numbers Say: 2025–2026 Usage Insight
Current 2025–2026 search results and grammar content show that “13rd vs 13th” remains a recurring question, especially among English learners and people checking dates, birthdays, rankings, and other ordinal forms. Recent grammar guides consistently explain the same standard rule: 13th is correct, while 13rd is incorrect.
This ongoing confusion happens because learners often apply the visible pattern of 3rd, 23rd, and 33rd too broadly. Therefore, understanding the 11–13 exception is more useful than simply memorizing individual examples.
The Most Common Ordinal Number Mistake
The most common problem is using only the last digit to choose the suffix.
For example:
- 23 → ends in 3 → 23rd
- 33 → ends in 3 → 33rd
- 13 → looks like it should be 13rd → but it is 13th
The reason is that 13 belongs to the special 11–13 exception group.
How to Avoid the Mistake
Use this quick two-step method:
- Check whether the number ends in 11, 12, or 13.
- If yes, use th. Otherwise, apply the normal last-digit rule.
This method works for all larger numbers too.
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How to Use 13th Correctly in Different Contexts
The correct form remains 13th in both British and American English. There is no regional spelling difference between the two forms in this case.
13th in American English
American English often uses:
- July 13
- July 13th
- the 13th of July
The style may vary depending on the context, but whenever an ordinal suffix is used, it must be 13th.
13th in British English
British English commonly uses:
- 13 July
- the 13th of July
- 13th July
Again, the ordinal form is always 13th.
13th Written in Words
When you spell it out completely, write:
thirteenth
Examples:
- The thirteenth chapter
- Her thirteenth birthday
- He came thirteenth in the competition
Cambridge Dictionary confirms that thirteenth is the written-word form of 13th.
13th vs 23rd: Why Are They Different?
This is where many people become confused. Both numbers contain or end with 3, but they follow different rules.
13th
The number 13 is part of the special exception:
13 → 13th
23rd
The number 23 is not part of the 11–13 exception group. Its final digit is 3, so it uses:
23 → 23rd
Compare these examples:
- 13th day ✔
- 23rd day ✔
- 33rd day ✔
- 113th day ✔
- 123rd day ✔
The best rule is this: look at the last two digits first.
Common Mistakes to Avoid When Writing Ordinal Numbers
Ordinal numbers may look simple, but several mistakes happen when people write quickly.
Mistake 1: Writing 13rd
Incorrect:
- She finished 13rd.
Correct:
- She finished 13th.
Mistake 2: Looking Only at the Last Digit
Incorrect thinking:
- 13 ends in 3, so it must use rd.
Correct thinking:
- 13 ends in 13, and numbers ending in 13 use th.
Mistake 3: Confusing Cardinal and Ordinal Numbers
A cardinal number shows quantity:
- thirteen books
- thirteen students
An ordinal number shows position:
- the 13th book
- the 13th student
Mistake 4: Using 13th Incorrectly as a Quantity
Incorrect:
- I have 13th books.
Correct:
- I have 13 books.
Use 13th only when you are showing order, position, rank, or sequence.
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A Quick Checklist for Choosing the Correct Ordinal Suffix
Before writing an ordinal number, use this checklist:
- Does the number end in 11? → Use th
- Does it end in 12? → Use th
- Does it end in 13? → Use th
- Otherwise, does it end in 1? → Use st
- Does it end in 2? → Use nd
- Does it end in 3? → Use rd
- All other numbers → Use th
Therefore:
- 1st
- 2nd
- 3rd
- 4th
- 11th
- 12th
- 13th
- 21st
- 22nd
- 23rd
- 24th
- 111th
- 112th
- 113th
Quiz 1: Quick Pick!
Which one is correct?
13rd or 13th?
Answer: 13th ✔
Quiz 2: Spot the Mistake!
Which sentence is correct?
A) Today is my 13rd birthday.
B) Today is my 13th birthday.
Answer: B) Today is my 13th birthday. ✔
Quiz 3: Fill the Gap!
She finished in ______ place.
A) 13rd
B) 13th
Answer: B) 13th ✔
Quiz 4: True or False?
13rd is a correct English ordinal number.
Answer: False ✔
Quiz 5: Date Challenge!
Which is correct?
A) July 13rd
B) July 13th
Answer: B) July 13th ✔
Quiz 6: Why 13th?
Why does 13 use th?
A) It is a special ordinal exception
B) All numbers use rd
Answer: A) It is a special ordinal exception ✔
Quiz 7: Word Power!
What is 13th written in words?
A) Thirteen
B) Thirteenth
C) Thirteenrd
Answer: B) Thirteenth ✔
Quiz 8: Choose the Right Suffix!
Which suffix does 13 use?
A) st
B) nd
C) rd
D) th
Answer: D) th ✔
Quiz 9: Birthday Test!
Complete the sentence:
“Happy ______ birthday!”
A) 13rd
B) 13th
Answer: B) 13th ✔
Quiz 10: Exception Check!
Which numbers are part of the special ordinal rule?
A) 11, 12, and 13
B) 1, 2, and 3
Answer: A) 11, 12, and 13 ✔
Quiz 11: Rank It Right!
He came ______ in the competition.
A) 13rd
B) 13th
Answer: B) 13th ✔
Quiz 12: Which One Is Different?
Which form is incorrect?
A) 3rd
B) 13rd
C) 23rd
Answer: B) 13rd ✔
Quiz 13: Number Challenge!
Which number correctly uses rd?
A) 13th
B) 23rd
C) 113th
Answer: B) 23rd ✔
Quiz 14: Fast Grammar Check!
What should you write?
“The ______ chapter is my favorite.”
A) 13rd
B) 13th
Answer: B) 13th ✔
Quiz 15: Final Boss!
Which rule is correct?
A) Every number ending in 3 uses rd
B) Numbers ending in 13 use th
Answer: B) Numbers ending in 13 use th ✔
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FAQs
Q. Is 13rd or 13th correct?
A: 13th is correct. The form 13rd is always incorrect in standard English.
Q. Why is 13th correct and not 13rd?
A: Because numbers ending in 11, 12, and 13 use the suffix th. The number 13 is an exception to the usual “numbers ending in 3 use rd” pattern.
Q. Is 13rd ever correct?
A: No. 13rd is not a correct standard English ordinal form.
Q. What is the correct spelling of 13th?
A: The correct word form is thirteenth.
Q. Do all numbers ending in 3 use rd?
A: No. For example:
- 3rd ✔
- 23rd ✔
- 33rd ✔
- 13th ✔
- 113th ✔
Numbers ending in 13 are exceptions.
Q. Is 13th used in both American and British English?
A: Yes. Both American and British English use 13th as the correct ordinal form.
Q. Should I write July 13 or July 13th?
A: Both can be correct depending on the writing style. However, if you use an ordinal suffix, write 13th, never 13rd.
Conclusion:
The answer to 13rd vs 13th is clear: 13th is the only correct form. The word form is thirteenth, and 13rd should never be used in standard English.
The confusion happens because 13 ends in 3. However, the ordinal suffix rule has an important exception: numbers ending in 11, 12, and 13 always use “th.”
So remember:
13th, not 13rd.
If you ever feel unsure, check the last two digits first. This simple habit will help you use ordinal numbers correctly in dates, rankings, birthdays, chapters, and everyday writing.
Keep learning with more easy grammar lessons on: Gramixo.com
Hi, I’m Bilal Khalid, the founder of Gramixo. I’m passionate about helping people improve their English through clear, practical, and easy-to-follow grammar content. By combining my experience in SEO with a focus on creating helpful educational resources, I publish guides that simplify Grammar rules, explain common mistakes, and improve writing skills. Whether you’re a student, a professional, or an English learner, my goal is to make learning grammar easier, more enjoyable, and genuinely useful in everyday life.
