What is the largest number supported?

The ordinal suffix and word outputs support numbers up to 1 trillion (1,000,000,000,000). Roman numerals are only generated for 1–3999.

Does it handle negative numbers or decimals?

No — ordinals are only defined for positive integers. Negative or decimal inputs will show an error message.

What does batch mode do?

Paste one number per line into the batch input area and click Convert All to get the ordinal, ordinal word, and Roman numeral for every number at once.

Why does Roman numeral stop at 3999?

Standard Roman numeral notation does not have an established symbol for numbers 4000 and above, so the tool marks those as N/A.

Number to Ordinal Converter

このツールについて

Convert any integer up to one trillion into its ordinal suffix (1st, 2nd, 3rd…), its full ordinal word (first, second, third…), and its Roman numeral representation for values up to 3999. Paste a list of numbers to convert them all at once in batch mode. Useful for sorting logic, reports, ranking systems, and educational content.

使い方

1 Type a number into the input field and press Convert (or Enter).
2 See the ordinal suffix (e.g. 42nd), ordinal word (forty-second), and Roman numeral.
3 For multiple numbers, switch to Batch Mode, enter one number per line, then click Convert All.
4 Copy any result with the copy button.

Ordinal versus cardinal: position, not quantity

A cardinal number answers "how many" — three apples, forty-two pages. An ordinal number answers "which position" — the third apple, the forty-second page. English marks ordinals two ways: with a numeric suffix (3rd, 42nd) and as a written word (third, forty-second). This tool produces both, plus the Roman-numeral form, from any integer you type. The conversions are subtler than they look, because English ordinals carry irregular spellings and the suffix follows a rule that trips up a surprising amount of software.

The suffix rule, stated exactly

The four possible suffixes are -st, -nd, -rd, and -th. The naive guess — "1 takes st, 2 takes nd, 3 takes rd, everything else th" — is wrong, and the place it breaks is the teens. The correct rule, which this tool implements, has two layers:

Check the last two digits first. If the number ends in 11, 12, or 13, the suffix is always -th: 11th, 12th, 13th, and likewise 111th, 512th.
Otherwise, check the last digit. Ending in 1 → st, in 2 → nd, in 3 → rd, anything else → th.

That two-step order is why 21st and 101st are correct but 11st is not. The teens exception exists because "eleventh," "twelfth," and "thirteenth" never sounded like "one-th" patterns in spoken English, and the written suffix follows the sound.

A worked example

Enter 1942. The tool inspects the last two digits — 42 — which is not in the 11–13 band, so it falls to the last-digit rule. The last digit is 2, giving the suffix form 1942nd. For the word form it converts the number to "one thousand nine hundred forty-two," then rewrites only the final word as an ordinal: one thousand nine hundred forty-second. Because 1942 is within 1–3999, it also renders the Roman numeral MCMXLII. Try 1913 instead and the last two digits 13 force the -th path: 1913th, one thousand nine hundred thirteenth.

How the word form handles round numbers

Ordinal words are not just the cardinal word with "-th" stapled on. The tool special-cases the irregular roots: 20 becomes twentieth (not "twenty-th"), 30 → thirtieth, 40 → fortieth, and multiples of larger units shift too — 100 → hundredth, 1000 → thousandth, a million → millionth. For a number like 42 it keeps the leading word intact and only ordinalises the tail: forty-second. Negatives are prefixed with "negative" and zero maps to zeroth.

Why Roman numerals stop at 3999

Standard Roman notation uses M for 1000 as its largest single symbol, and the convention only repeats a symbol up to three times. That caps the writable range at 3999 = MMMCMXCIX. Beyond that you would need a vinculum (an overbar meaning "times 1000"), which has no agreed plain-text form, so the tool returns N/A for 4000 and above, and for any value below 1. The greedy algorithm it uses is the standard one: subtract the largest fitting value repeatedly, which automatically produces the subtractive forms like IV (4), IX (9), and XL (40).

Batch mode and real use cases

Switch to batch mode to paste a whole column of numbers — one per line — and get a table of suffix, word, and Roman forms for all of them at once. This is the practical heart of the tool for anyone generating text programmatically by hand: writing out "1st, 2nd, 3rd…" labels for a leaderboard, numbering chapters or appendices, producing anniversary or edition language ("the 25th edition," "the 50th anniversary"), or building copy where the spelled-out form reads better than digits ("our fortieth year"). The maximum supported magnitude is one trillion; larger inputs return a clear error rather than a wrong answer.

Common mistakes this tool avoids

The teens trap. Hand-written code and spreadsheets routinely emit 11st, 12nd, 13rd. The two-digit check here prevents that.
Hyphenation. Compound ordinals are hyphenated (forty-second, ninety-ninth), which the word output preserves.
Expecting decimals or fractions. Ordinals describe whole positions only; a non-integer or out-of-range input shows an error instead of guessing.
Assuming Roman numerals scale. They do not past 3999 — if you need 4000+, the suffix and word forms still work, but the Roman column will read N/A by design.