You’re writing an invitation and you freeze. Is it 13th or 13rd? Here’s the answer right away. It’s 13th, every single time. The 13rd vs 13th mix-up is a common spelling mistake and it happens for a good reason. Numbers like 23rd and 33rd end in rd so 13 feels like it should too.
Here’s the catch. English treats 11th, 12th, and 13th as special cases. They all take th, no matter what the last digit says. This guide breaks down the rule in plain words. You’ll see real examples for dates, birthdays, and anniversaries. You’ll also learn how to spell it out as thirteenth and how to avoid the slip next time. By the end the confusion will disappear for good. It takes about five minutes. You won’t need a grammar degree either. Ready? Let’s sort it out together.
13rd vs 13th: Which Spelling Is Correct?
13th is the correct one. It’s the standard correct ordinal form for thirteen and you read it aloud as thirteenth. The 13rd spelling shows up often but it’s a spelling error that no dictionary or style guide accepts.
So why does the wrong version feel right? Because 23rd, 33rd, and 43rd all end in rd. Your eyes spot a 3 at the end and your fingers add rd on autopilot.
Here’s the fix in one line. Teens always take th. Lock that in and the 13rd spelling mistake stops happening.
Why Is 13th Correct Instead of 13rd?
Start with what English ordinal numbers do. They show position or order, like first, second, or third. English then picks an ending based on the last-digit rule.
A number ending in 1 takes the st suffix. Ending in 2 takes the nd suffix. Ending in 3 takes the rd suffix. Everything else takes the th suffix.
Now the real reason. The numeral copies the spelled-out word. Twenty-third ends in rd, so you write 23rd. Thirteenth ends in th, so you write 13th.
The history backs this up. In Old English, thirteen was a compound structure that meant three and ten. The word for ten was tien. Speakers added th to the whole compound. Nothing in that story ever produced rd.
This table shows the last-digit rule and the one group that breaks it.
| Last digits | Suffix | Example | Spelled out |
| 1 (not 11) | st | 21st | twenty-first |
| 2 (not 12) | nd | 32nd | thirty-second |
| 3 (not 13) | rd | 43rd | forty-third |
| 11, 12, 13 | th | 13th | thirteenth |
| 0, 4 to 9 | th | 14th | fourteenth |
Look at the third row. Only a 3 that isn’t part of 13 earns rd. The teen exception overrides the pattern for 11, 12, and 13.
Why Do 11th, 12th, and 13th All Use “Th”?
These three trip up the most writers. They end in 1, 2, and 3, so the usual endings look tempting. Yet eleventh, twelfth, and thirteenth all finish with th.
English treats teen numbers as one unit. Eleven and twelve don’t sound like ten plus one or two. Compare that with twenty-three, where the 3 stands alone as its own word.
That’s how 13nd or 13st and thirteenrd sneak in. Each one follows the last digit and ignores the word behind it.
Here’s the teen run at a glance:
- 11th (eleventh)
- 12th (twelfth)
- 13th (thirteenth)
- 14th through 19th (fourteenth through nineteenth)
Every one of them ends in th. No exceptions.
How to Write 13th in Words
Write it as thirteenth. That’s one word with no hyphen and no space. It’s the correct spelled-out version for a poem or a legal memo.
Say it slowly and you’ll hear three parts: thir, teen, and th. The numeral gets pronounced thirteenth, so what you say matches what you write.
Watch the neighbor too. Thirty-third takes a hyphen because it joins two number words. Thirteenth doesn’t, since it’s a single word.
How to Use 13th in Dates, Birthdays, and Anniversaries
Real writing happens in invitations, calendars, and cards. The rule stays the same everywhere. These quick cases prove it.
The suffix doesn’t care about word order. Both the 13th of March and June 13th are correct. In US writing you can even drop the suffix and write June 13.
October 13th or 13rd
It’s October 13th. Never October 13rd. Picture a book club notice: Our next meeting is October 13th at 7 p.m.
Writers often pause on October 13rd or 13th right before they hit send. Don’t. The answer is th, always.
July 13th or 13rd
It’s July 13th. Imagine a travel plan that reads: We land in Lisbon on July 13th. Swap the month and the suffix stays put.
That settles any July 13rd or 13th doubt in a calendar entry.
13th or 13rd Birthday
It’s a 13th birthday. For many kids it marks the jump into the teen years, so the number lands on cakes and banners.
A banner that reads Happy 13th Birthday, Mia looks right. One with 13rd draws raised eyebrows. If you’re weighing 13rd or 13th birthday wording, pick 13th and print with confidence.
13th or 13rd Anniversary
It’s a 13th anniversary. Lace is the traditional gift for year thirteen and couples often work it into the card too.
Check the spelling before any engraving starts. Metal doesn’t have an undo button. The 13rd or 13th anniversary question has the same answer as every other date: 13th.
13th vs 13rd: Correct and Incorrect Examples
Seeing both forms side by side helps. This table pairs real-life examples with the usual slip.
| Situation | Correct | Incorrect |
| Invitation | Join us on October 13th. | Join us on October 13rd. |
| Calendar | Dentist on July 13th | Dentist on July 13rd |
| Birthday card | Happy 13th birthday! | Happy 13rd birthday! |
| Anniversary | Our 13th anniversary | Our 13rd anniversary |
| Sports | His 13th goal | His 13rd goal |
| Building | The 13th floor | The 13rd floor |
Every wrong version looks believable at a glance. That’s the trap. Read the correct column out loud and your ear will back up your eyes.
Imagine a banner for a 13rd anniversary party. Reprinting costs money and patience. A ten-second check costs nothing.
Does the Same Rule Apply to 113th, 213th, and Other Numbers?
Yes, it does. The rule looks at the last two digits and not just the last one. Any number ending in 13 takes th. That covers 113th, 213th, and 1,013th.
The same goes for 111th and 112th, plus 211th and 212th. They all end in a teen pair so th wins. Meanwhile 23rd, 33rd, and 43rd keep rd because they aren’t teens.
Be careful with numbers ending in 1, numbers ending in 2, and numbers ending in 3. They only take st, nd, or rd when the last two digits aren’t 11, 12, or 13.
Use this four-step check on any number:
- Look at the last two digits.
- If they read 11, 12, or 13, add th.
- If not, check the last digit: 1 takes st, 2 takes nd, and 3 takes rd.
- Everything else takes th.
Try it on 1,013. The last two digits read 13, so you write 1,013th.
Common Mistakes to Avoid When Writing 13th
Most slips fall into a few patterns. Watch for these in your own drafts:
- Using 13rd because the number ends in 3.
- Typing 13nd or 13st after guessing the suffix.
- Writing thirteenrd in full words.
- Mixing styles in one document, like 13th in one line and thirteenth in the next.
- Adding extras such as an apostrophe (13’th) or a space (13 th).
That last pair looks small but it hurts consistent formatting. Pick one style and stick with it.
Why Spellcheck and Autocorrect Miss 13rd
Here’s the sneaky part. Many spellcheck tools skip any token that contains digits. Microsoft Word, for one, has an Ignore words with numbers option that’s usually switched on. So 13rd often gets no red underline.
Those autocorrect blind spots explain why polished documents still carry a spelling error like this. A human read-through catches what software shrugs off.
Before you publish, search your file for 13rd, 12nd, and 11st. It takes ten seconds.
Where 13th Shows Up: History, Religion, and Culture
The number carries weight beyond calendars. You’ll meet it in textbooks, buildings, and scripture, so spelling it right matters. These are the historical and religious uses of 13th you’ll see most:
- 13th century: the years 1201 to 1300, which include the Magna Carta in 1215.
- 13th Amendment: the change to the U.S. Constitution that abolished slavery. It was ratified in December 1865.
- 13th floor: many buildings skip the label and jump from 12 to 14.
- Last Supper: Jesus and his twelve disciples made thirteen at the table, a detail often tied to the number’s unlucky image.
- 13th chapter or verse: 1 Corinthians 13 is a famous example.
Superstition adds fuel. Friday the 13th still makes people nervous. In 2026 it lands three times, on February 13th, the 13th of March, and November 13th.
Everyday speech uses it too, like the 13th time you rewatch a favorite show. Whatever the setting, th stays.
13th in Formal, Casual, Academic, and Business Writing
Where you write changes how you format 13th. It never changes how you spell it. This table shows the common choices.
| Writing type | Common style | Example |
| Formal writing | Spell out the word in running text | The firm’s thirteenth anniversary |
| Casual writing | Use numerals | See you on the 13th! |
| Academic writing | Follow the assigned style guide | Chicago spells out ordinals up to one hundred |
| Business documents | Numerals in dates and lists | Due July 13th |
Newsrooms that follow AP style spell out first through ninth and switch to figures from 10th. So 13th stays numeric there.
Whatever you pick, stay consistent inside one document. Both 13th and thirteenth are the accepted form. The grammatically acceptable choice never includes 13rd.
Easy Ways to Remember 13th vs 13rd
Rules stick better with a hook. Try one of these tricks to remember 13th vs 13rd:
- Teens end in th. Thirteen sounds like ten and ten’s family takes th.
- Say the full word. Thirteenth ends in th and the numeral mirrors it.
- Think teen first. If you see 13, ignore the 3 and add th.
- Spot the odd one out. A 3 only gets rd when it stands alone, as in 23rd.
Which trick works for you? Drop it in the comments. Then share this guide with a friend who plans events.
Frequently Asked Questions About 13rd vs 13th
Is It 13th or 13rd?
It’s always 13th. The 13rd vs 13th debate ends here, because teen numbers take th no matter the last digit.
Is It Correct to Say 13th?
Yes, 13th is correct and standard. In the 13rd vs 13th choice, 13th wins and you read it as thirteenth.
Is 13rd Ever Correct in Standard English?
No. In the 13rd vs 13th question, 13rd is always a spelling error and no major style guide accepts it.
How Do You Write 13th in Full Words?
Write thirteenth as one word. For 13rd vs 13th, the spelled-out form is thirteenth with no hyphen and no space.
Conclusion
The 13rd vs 13th question has one clear answer. It’s 13th. Teen numbers follow their own rule so 11th, 12th, and 13th all take th. That’s why 13rd is a spelling error. You can now settle any 13rd vs 13th debate in seconds. Just check the last two digits first. If they read 13, write th and move on.
Keep this 13rd vs 13th guide handy for invites, birthdays, and reports. It also works for 113th and 213th. Try the memory tricks on a friend and see if they spot the slip. Did this clear up your 13rd vs 13th doubts? Drop your thoughts in the comments. Share it with someone who writes a lot of dates. A small fix like this makes your writing look polished. Next time you type 13th you’ll get it right without thinking. Happy writing, friend
