Build your Roman Numeral Converter with AI in under 5 minutes

Build a Roman numeral converter that turns numbers into Roman numerals and back — type a number (1–3999) to get the numeral or a numeral to get the number, with strict canonical validation and a symbol chart. Runs in the browser.

仕組み

ステップ 1

アイデアを入力

作りたいものを自然な文章で入力してください。

ステップ 2

AIがビルド

FloopFloopが本番対応コードを即座に生成します。

ステップ 3

デプロイして公開

数分以内に専用サブドメインでプロジェクトが公開されます。

開発者を採用する代わりにAIでビルドする理由

FloopFloop従来の開発者
リリースまでの時間5分未満2〜8週間
費用$0から$5,000〜$50,000以上
メンテナンスプランに含まれる継続的な保守契約

What is a roman numeral converter?

A Roman numeral converter turns an ordinary number into the I-V-X-L-C-D-M letters the Romans used, and decodes them back again. Seven symbols stand for values, you add them largest-to-smallest, and the clever bit is subtractive notation — a smaller letter before a larger one means subtract, so four is IV rather than IIII. People reach for a converter constantly even though the system looks simple: working out the year carved on a building or stamped in a film's credits, formatting a date for a tattoo or invitation, numbering chapters and appendices, or setting a clock face. The standard range runs 1 to 3999, since there's no single letter bigger than M. What separates a good converter from a sloppy one is strictness — accepting only the canonical spelling and rejecting forms like IIII or VV — and making it effortless to go both directions.

Common features

  • Number to Roman numeral and back
  • Auto-detects which way you're converting
  • Proper subtractive notation (IV, IX, XL, XC, CD, CM)
  • Strict canonical validation (rejects IIII, VV, IC)
  • Covers the standard 1–3999 range
  • A chart of the seven symbols
  • Case-insensitive numeral input
  • One-click copy of the result
  • Everything client-side; input remembered
  • Light and dark themes

Real-world examples

A year on a building

Someone reads MCMXCIV off a cornerstone, types it in, and learns the building dates to 1994.

A date for a tattoo

A user converts 2024 to MMXXIV to lay out a clean Roman-numeral date.

Catching a bad numeral

Someone types IIII and the converter flags it as invalid, nudging them to the correct IV.

Why FloopFloop fits roman numeral converter projects

A Roman numeral converter is a tiny, classic tool you want instant, ad-free, and yours. FloopFloop ships the converter you want — a date mode, larger ranges with a vinculum, your own engraved styling — on your own domain, with every conversion running in the browser. The carved 'stone inscription' that ships by default renders the result like a real Roman engraving, and the whole thing is one prompt away from being whatever fits your idea.

試してみてください

以下のプロンプトをコピーしてFloopFloopに貼り付けてお使いください。

Build a Roman numeral converter with a single smart input that auto-detects direction: type a number (1–3999) to get its Roman numeral, or type a numeral to get the number. Use proper subtractive notation (4 = IV, 9 = IX, 40 = XL, 90 = XC, 400 = CD, 900 = CM), and validate strictly so non-canonical forms like IIII or VV are rejected. Render the result large in a serif like a carved inscription, with a copy button, and show a chart of the seven symbols (I V X L C D M) below. Keep it deterministic so the first render is hydration-safe, and remember the input in localStorage. 100% client-side.

Create a tool to convert numbers to Roman numerals and Roman numerals to numbers, with a reference chart. Keep it in the browser.

Build a Roman numeral converter for dates and tattoos — type a year and get the numeral — with a clean classical look and a dark theme.

Build a number-to-Roman-numeral converter that also decodes numerals back to numbers and rejects invalid ones.

よくある質問

What range does it cover?
The standard 1 to 3999. There's no single Roman letter larger than M (1000), so 3999 (MMMCMXCIX) is the largest value writable with the classic symbols and subtractive notation.
What is subtractive notation?
Putting a smaller symbol before a larger one to mean 'subtract' — so 4 is IV (one less than five) rather than IIII, and 9 is IX. The six subtractive pairs are IV, IX, XL, XC, CD, and CM. The converter produces and requires this canonical form.
Does it reject invalid numerals?
Yes — it only accepts the canonical spelling. IIII, VV, and IC are rejected because the correct forms are IV, X, and XCIX. Decoding round-trips through the encoder, so anything that wouldn't be produced is refused.
How do I write a year as a Roman numeral?
Just type the year — 2024 becomes MMXXIV, 1994 becomes MCMXCIV. It's handy for dates on buildings, film credits, clock faces, and tattoos.
Is anything uploaded?
No. Every conversion runs in your browser and your last input is saved to localStorage only. The single outbound surface is the /api/health probe.

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