Rank With Ordinal Suffix: How to Format 1st, 2nd, 3rd

This calculator adds the correct ordinal suffix (st, nd, rd, th) to any positive whole number, turning 1 into 1st, 2 into 2nd, 3 into 3rd, and 4 into 4th. You enter a number (or a list of numbers) and get back the properly formatted ordinal form, ready for dates, rankings, or any written list. The rule is simple, but English has a few quirks that trip people up—this tool handles them automatically.

Formula

The ordinal suffix depends on the last two digits of the number, not just the last one. The general rule is:

• If the number ends in 1 (but not 11) → add st (e.g., 1st, 21st, 101st)
• If the number ends in 2 (but not 12) → add nd (e.g., 2nd, 22nd, 102nd)
• If the number ends in 3 (but not 13) → add rd (e.g., 3rd, 23rd, 103rd)
• All other numbers → add th (e.g., 4th, 11th, 12th, 13th, 20th, 100th)

In the calculator above, the function suffix(n) applies this rule. For a number n, the suffix is determined by n mod 100 (the last two digits). If that value is 11, 12, or 13, the suffix is always “th”. Otherwise, look at n mod 10 (the last digit): 1→st, 2→nd, 3→rd, everything else→th.

Worked Example

Using the default value of 7:

1. Check the last two digits: 07. That is not 11, 12, or 13.
2. Check the last digit: 7.
3. 7 is not 1, 2, or 3, so the suffix is th.
4. Result: 7th.

The calculator shows “7th” as the answer, matching the rule.

When to Use Ordinal Suffixes

Ordinal numbers show position or order in a sequence. You use them in:

• Dates: “January 1st” or “the 3rd of March” (though many style guides prefer “1” without the suffix in full dates—see below).
• Rankings: “He finished 2nd in the race,” “She is the 5th person in line.”
• Floors and levels: “The office is on the 21st floor.”
• Centuries and anniversaries: “The 21st century,” “their 50th wedding anniversary.”
• Fractions in speech: “a 3rd of the cake” (though “third” is usually written out).

In formal writing, numbers under ten are often spelled out (“second place” not “2nd place”), but the suffix form is common in tables, lists, and casual contexts.

Common Mistakes and Exceptions

The biggest error is applying the simple rule to 11, 12, and 13. They are the exceptions:

• 11th – not 11st
• 12th – not 12nd
• 13th – not 13rd

This happens because the rule is based on the last two digits, not the last one. For example, 111 ends in 11, so it is 111th, not 111st. Similarly, 212 is 212th, not 212nd. Always check the last two digits first.

Another common mistake is mixing up ordinal and cardinal numbers. “1st” is ordinal (position), while “1” is cardinal (quantity). “He came 1st” is correct; “he came 1” is not.

In dates, many style guides (like APA and Chicago) recommend writing “January 1” without the suffix, but “January 1st” is widely accepted in informal writing. The suffix is mandatory when the day stands alone: “I’ll see you on the 1st.”

How to Choose the Right Suffix in Your Head

If you don’t have a calculator handy, use this mental shortcut:

1. Look at the last two digits. If they are 11, 12, or 13, the suffix is th.
2. Otherwise, look at the last digit only.
3. Last digit 1 → st; 2 → nd; 3 → rd; anything else → th.

For example, 1023: last two digits are 23, not 11/12/13. Last digit is 3, so it’s 1023rd. 1042: last two digits 42, last digit 2 → 1042nd. 1011: last two digits 11 → 1011th.

Limits of the Rule

This rule works for all positive integers. It does not apply to:

• Negative numbers: Ordinals are not used with negative numbers in normal English.
• Zero: “0th” is sometimes used in computing (e.g., “the 0th element”), but it is not standard English. The rule would give “0th” because 0 ends in 0, which takes “th”.
• Decimals: You don’t write “3.5th”. You say “third and a half” or “the fourth” (rounding).
• Roman numerals: Those are written as “IV” not “4th”.

Also note that in some languages, ordinals change form based on gender or case (e.g., Spanish “primero” vs. “primera”). This calculator only handles English.

Frequently Asked Questions

Why is it 11th and not 11st?

Because the rule depends on the last two digits. The number 11 ends in “11”, which is an exception. The same applies to 12 and 13. This is a historical quirk of English pronunciation: “eleventh”, “twelfth”, and “thirteenth” have always used the “th” sound, so the written suffix follows.

Do I need a suffix on dates like “May 1”?

In formal writing, no. Most style guides prefer “May 1” (without the suffix) when the month is named. But when the day stands alone, you must write “the 1st”. In informal writing, “May 1st” is fine and common.

What about numbers like 21, 22, 23?

They follow the normal rule because they do not end in 11, 12, or 13. So 21st, 22nd, 23rd. The exception only applies when the last two digits are exactly 11, 12, or 13.

Is “0th” correct?

It is used in technical contexts (like array indexing in programming), but it is not standard English. In everyday language, you would say “zeroth” (which is spelled with a “th”), but it’s rare. The calculator will output “0th” if you enter 0, which is fine for technical use.

How do I write ordinal numbers in words?

For numbers under ten, write them out: first, second, third, fourth, etc. For larger numbers, you can use digits with the suffix (21st) or write them out (twenty-first). In formal writing, consistency is key—pick one style and stick to it.

Does this rule work for very large numbers?

Yes, as long as the number is a positive integer. The last two digits determine the suffix, so 1,000,001st is correct (ends in 01, so “st”), and 1,000,011th is correct (ends in 11, so “th”).

Related

• Mouse Sensitivity Randomly Changes? Fixes That Work
• Headphones vs Headsets vs Earbuds: What’s the Difference?
• Max by Month: Average Baby Weight & Growth

in n | Number | - | 7 | 0
out ordinal | Ordinal form | - | n + suffix(n) | 0