Ordinal numbers.

Worked example

For 23 the tens digit is 2, not 1, so the units digit decides: 3 takes "rd", giving 23rd. In words only the last word changes: twenty-three becomes twenty-third. For 112 the tens digit is 1, so it is 112th (one hundred twelfth), the same way 11th, 12th and 13th work.

How it works

The suffix rule: if the last two digits are 11, 12 or 13, use "th" (11th, 12th, 13th, 111th). Otherwise the last digit decides: 1 gives "st", 2 gives "nd", 3 gives "rd", and 0 or 4 to 9 give "th".

In words, only the final word of the number becomes an ordinal. The irregular ones are first, second, third, fifth, eighth, ninth, twelfth and twentieth; words ending in -y change to -ieth (thirtieth, ninetieth); the rest add -th (fourth, sixth, hundredth, thousandth, millionth). Zero is "zeroth", used in zero-based counting.

Numbers up to 24 digits are supported, and the list mode shows up to 1,000 numbers at once.

Sources and basis (opened 2026-10-15): English numerals - Wikipedia (irregular ordinal forms, the 11/12/13 "th" rule and the suffix by last digit).

FAQ

Why is it 11th, 12th and 13th, not 11st, 12nd and 13rd?

Numbers ending in 11, 12 or 13 always take "th". That rule also applies to 111th, 112th and 1,013th.

What is 21 as an ordinal?

21st, written out as twenty-first.

How do you spell the ordinals 5, 8, 9 and 12?

Fifth, eighth, ninth and twelfth. These are irregular, so the tool uses a fixed list for them.

What is the ordinal for 100 and 1,000?

One hundredth (100th) and one thousandth (1,000th).

What is "zeroth"?

An ordinal for zero, used only in zero-based counting such as mathematics or computing.