The confusion between 13rd vs 13th is a common grammar and numbering mistake. Many people know that numbers like 1st, 2nd, and 3rd use special endings, but they sometimes apply those endings incorrectly to larger numbers.
If you’re wondering whether to write 13rd or 13th, the answer is simple: only one form is correct.
Quick Answer
✅ 13th is correct.
❌ 13rd is incorrect.
Correct example:
- “Her birthday is on the 13th of June.”
Incorrect example:
- “Her birthday is on the 13rd of June.”
Always use 13th when writing the ordinal form of 13.
What Does 13th Mean?
Mathematics 13th is the ordinal form of the number 13.
Ordinal numbers show:
- position
- order
- rank
- sequence
Examples
- The 13th day of the month
- The 13th chapter of a book
- The 13th contestant
- The 13th anniversary
Why Is 13rd Incorrect?
People sometimes assume that because 3 → 3rd, then 13 → 13rd.
However, English ordinal numbers follow a special rule for numbers ending in 11, 12, and 13.
Correct Forms
| Number | Ordinal Form |
|---|---|
| 11 | 11th |
| 12 | 12th |
| 13 | 13th |
Even though 13 ends in the digit 3, it still takes -th.
13rd vs 13th: Main Difference
| Form | Correct? | Usage |
|---|---|---|
| 13th | ✅ Correct | Ordinal form of 13 |
| 13rd | ❌ Incorrect | Grammar and numbering error |
Ordinal Number Rules
Most English ordinal numbers use:
- st
- nd
- rd
- th
Basic Pattern
| Number | Ordinal |
|---|---|
| 1 | 1st |
| 2 | 2nd |
| 3 | 3rd |
| 4 | 4th |
| 5 | 5th |
Important Exception
Numbers ending in:
- 11
- 12
- 13
always use th.
Examples
- 11th ✅
- 12th ✅
- 13th ✅
Not:
- 11st ❌
- 12nd ❌
- 13rd ❌
Examples of 13th in Sentences
- Today is the 13th of October.
- She finished in 13th place.
- The meeting will be held on the 13th.
- This is the 13th chapter of the novel.
Common Mistakes People Make
Mistake 1: Writing 13rd
Incorrect:
- 13rd birthday
Correct:
- 13th birthday
Mistake 2: Following the Last Digit Only
Many people focus on the final digit (3) and incorrectly choose rd.
Remember that 13 belongs to the exception group.
Mistake 3: Confusing Cardinal and Ordinal Numbers
| Type | Example |
|---|---|
| Cardinal Number | 13 |
| Ordinal Number | 13th |
Ordinal Number Chart
| Number | Correct Ordinal |
|---|---|
| 10 | 10th |
| 11 | 11th |
| 12 | 12th |
| 13 | 13th |
| 14 | 14th |
| 20 | 20th |
| 21 | 21st |
| 22 | 22nd |
| 23 | 23rd |
| 24 | 24th |
This chart shows why 13th is correct.
American vs British English Differences
Both:
- United States American English
- United Kingdom British English
use:
✅ 13th
There is no spelling or grammar difference.
Why Correct Ordinals Matter
English Grammar Correct ordinal numbers improve:
- writing accuracy
- professionalism
- readability
- credibility
Mistakes such as 13rd can look unprofessional in formal documents, invitations, and business communication.
Easy Trick to Remember
Remember the Teen Exception
Numbers ending in:
- 11
- 12
- 13
always use th.
Memory tip:
11th, 12th, and 13th are a special team that always takes -th.
Related Examples
Correct
- 11th
- 12th
- 13th
- 14th
Incorrect
- 11st
- 12nd
- 13rd
- 14rd
FAQs
Which is correct: 13rd or 13th?
13th is correct.
Why is 13rd wrong?
Because numbers ending in 11, 12, and 13 always use -th, regardless of their final digit.
What is the ordinal form of 13?
The ordinal form is 13th.
How do you write the thirteenth day?
You can write it as 13th or thirteenth.
Is 23rd correct?
Yes. Since 23 does not end in 13, it follows the normal rule and takes rd.
Why doesn’t 13 use rd?
English treats 11, 12, and 13 as exceptions that always use th.
Do British and American English use different forms?
No. Both use 13th.
Can grammar checkers detect 13rd?
Yes. Most grammar and spell-check tools flag 13rd as incorrect.
Final Summary
The difference between 13rd vs 13th is straightforward. 13th is the correct ordinal form of 13, while 13rd is a grammatical error. Although the number ends in 3, English ordinal rules require 11, 12, and 13 to take the suffix -th.
Whether you’re writing dates, rankings, anniversaries, or lists, always use 13th. Following this simple rule will help you avoid one of the most common ordinal number mistakes.
Actionable Takeaway
Remember this rule:
- 13th = correct ✅
- 13rd = incorrect ❌
Also remember the special exception:
- 11th ✅
- 12th ✅
- 13th ✅
When writing the ordinal form of 13, always choose 13th.
