Roman Numeral Converter — Both Directions

Type 1–3999 or a Roman numeral (I–MMMCMXCIX) and get the other form instantly, with the breakdown shown.

Quick answer: Convert numbers to Roman numerals and back free: 1–3999 both directions with validation and a quick reference table. Instant, in-browser.

Number or Roman numeral

I=1 V=5 X=10 L=50 C=100 D=500 M=1000 · subtractive: IV=4 IX=9 XL=40 XC=90 CD=400 CM=900

How to use

Enter a number (1–3999) or Roman numeral.
Press Convert — the other form appears with breakdown.
Use the reference table below for study.

About this tool

Roman numerals appear in clocks, movie credits, chapters and monarch names. This converter handles both directions with proper subtractive notation (IV, IX, XL, CM), validates input strictly, and shows the additive breakdown so students see why 1994 = MCMXCIV. Local and instant, like all our tools. Your file never leaves this page — everything runs in your browser, there is no upload endpoint on this site, and the file is dropped from memory when you close the tab.

FAQ

Range?

1–3999 — classical Roman numerals have no zero and standard notation stops at 3999.

Why no 4000+?

Ancient notation used overlines for thousands-multipliers; we stick to the standard classroom form.

Lowercase input?

Accepted and normalized to uppercase.

Is 'IIII' valid?

No — subtractive form requires IV; clock faces use IIII as tradition, not maths.

Can I copy results?

One click.

How does the breakdown work?

Each digit maps to its place-value symbol group (900=CM, 40=XL…).

Rate this tool

Your rating stays in this browser (local storage) — nothing is sent to any server.

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The complete roman numeral converter guide

Prefer the long version — a worked example, the mistakes people actually make, and answers to real questions? The blog guide Roman Numeral Converter — Complete Guide, Mistakes & FAQ covers all of it step by step.

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Roman Numeral Converter — Both Directions

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