Have you ever typed “13rd” while writing a date or ranking and wondered if it looked right? It’s a common mistake because English ordinal numbers don’t always follow the patterns we expect. Many people know that 3 becomes 3rd, so it’s easy to assume that 13 should become 13rd—but that’s not how English grammar works.
If you’ve searched 13rd or 13th, this guide explains the correct form, why 13rd is incorrect, the rules for ordinal numbers, and simple tricks to help you remember the right suffix every time.
13rd or 13th: The Correct Answer
The correct form is:
13th
The form 13rd is always incorrect.
Examples:
- My birthday is on the 13th of June.
- She finished in 13th place.
- The meeting is scheduled for the 13th.
No matter the context, 13th is the only correct ordinal form of the number 13.
Why Is 13rd Incorrect?
The confusion usually comes from the number 3.
People know that:
- 3 → 3rd
So they mistakenly assume:
- 13 → 13rd
However, English ordinal numbers follow a special rule for numbers ending in 11, 12, and 13.
Even though 13 ends with the digit 3, its suffix is -th, not -rd.
That’s why:
- 11 → 11th
- 12 → 12th
- 13 → 13th
This is one of the most important exceptions in English numbering.
Understanding Ordinal Numbers
Ordinal numbers show position or order.
Unlike cardinal numbers, which count quantity, ordinals indicate rank.
Examples:
- First person
- Second place
- Third attempt
- Fourth chapter
- Thirteenth day
You’ll see ordinal numbers in:
- Dates
- Competitions
- Lists
- Addresses
- Anniversaries
- Book chapters
Ordinal Number Rules
English uses four common suffixes.
| Number | Ordinal |
| 1 | 1st |
| 2 | 2nd |
| 3 | 3rd |
| 4 | 4th |
| 5 | 5th |
| 6 | 6th |
| 7 | 7th |
| 8 | 8th |
| 9 | 9th |
| 10 | 10th |
The pattern continues for larger numbers—but with an important exception.
The Special Rule for 11, 12, and 13
The endings 11, 12, and 13 always use -th.
Correct examples:
- 11th
- 12th
- 13th
Incorrect examples:
- 11st
- 12nd
- 13rd
This rule applies regardless of the last digit.
Larger Numbers Follow the Same Rule
Once you understand the exception, larger numbers become easier.
Examples:
| Correct | Incorrect |
| 21st | 21th |
| 22nd | 22th |
| 23rd | 23th |
| 24th | 24rd |
| 31st | 31th |
| 32nd | 32th |
| 33rd | 33th |
Notice that only 11, 12, and 13 break the usual pattern.
When Do We Use 13th?
The ordinal 13th appears in many situations.
Dates
- January 13th
- July 13th
- December 13th
Many style guides also allow:
- January 13
Both are correct depending on the writing style.
Rankings
- She finished 13th in the marathon.
- Our team placed 13th overall.
Floors and Levels
- The office is on the 13th floor.
- We stayed in the 13th room.
Chapters and Sections
- Read the 13th chapter.
- The answer appears in the 13th section.
Common Mistakes
Many writers accidentally choose the wrong suffix.
Incorrect
13rd
Correct:
13th
Incorrect
12nd
Correct:
12th
Incorrect
11st
Correct:
11th
Learning these exceptions prevents one of the most common numbering mistakes.
Memory Trick
A simple trick makes the rule easy to remember.
Think:
11, 12, and 13 are a team.
They always end with:
TH
No exceptions.
Everything after that returns to the normal pattern.
For example:
- 21st
- 22nd
- 23rd
This single rule eliminates most ordinal number errors.
Why Do People Write 13rd?
Several factors contribute to the mistake.
The Number Ends in 3
People naturally associate:
3 → 3rd
So they assume:
13 → 13rd
Unfortunately, English doesn’t work that way.
Fast Typing
Many errors occur simply because people type quickly without thinking about ordinal rules.
Limited Exposure
Some people rarely write ordinal numbers, making it easier to forget the exceptions.
Tips for Using Ordinal Numbers Correctly
To avoid mistakes:
- Memorize the exception for 11th, 12th, and 13th.
- Read dates carefully before sending emails.
- Let spell-check catch obvious errors.
- Practice common ordinal numbers.
- Remember that suffixes indicate position, not quantity.
These habits improve both accuracy and confidence.
Key Takeaways
- 13th is the correct ordinal form.
- 13rd is always incorrect.
- Numbers ending in 11, 12, and 13 always use -th.
- Ordinal numbers indicate position or order.
- A simple memory trick can help you avoid this common grammar mistake.
Frequently Asked Questions
Is it 13rd or 13th?
The correct form is 13th. 13rd is not grammatically correct in English.
Why isn’t 13 written as 13rd?
Although 13 ends with the digit 3, English treats 11, 12, and 13 as exceptions. They always take the suffix -th.
Is 13rd ever correct?
No. 13rd is never considered correct in standard English writing.
What is the rule for ordinal numbers?
Most numbers ending in 1, 2, and 3 use -st, -nd, and -rd respectively, except for 11, 12, and 13, which always use -th.
How should I write dates?
You can write:
- June 13
- June 13th
Both are widely accepted, depending on the style guide you’re following.
Why do people confuse 13th and 13rd?
The confusion comes from the fact that 3 becomes 3rd, leading many writers to incorrectly assume that 13 becomes 13rd. Remembering the exception solves the problem.
Conclusion
Understanding 13rd or 13th is easier once you know the rule behind English ordinal numbers. While 3rd is correct for the number three, 13rd is always incorrect because 11, 12, and 13 are special cases that always take the suffix -th. Whether you’re writing a date, ranking, address, or chapter number, 13th is the only correct form.
Mastering this small grammar rule can make your writing look more polished and professional. The next time you reach the number 13, you’ll know exactly which suffix to use—and you’ll never second-guess it again.
