Roman Numeral Converter (Both Directions)

Input

Enter 1994 or MCMXCIV — either is recognised automatically.

Number or numeralNumbers 1–3,999,999 or valid Roman numerals

Notation for large values

RESULT

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Direction detected—

Valid?—

Number of symbols—

Subtractive pairs used—

Lowercase form—

Spoken as—

Symbol breakdown

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The seven symbols

I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. Every Roman numeral is built from these, largest first, adding as you go — except where subtraction applies.

The subtractive rule, stated precisely

A smaller symbol before a larger one means subtract, but only in six specific pairs: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). I can only precede V and X; X can only precede L and C; C can only precede D and M. V, L and D never subtract at all.

This is why IC is not 99 — a common guess, and invalid. 99 is XCIX: ninety (XC) followed by nine (IX). The validator above rejects malformed input rather than guessing at an intent.

Why 1994 is MCMXCIV

Split by place value: 1000 + 900 + 90 + 4. That is M + CM + XC + IV. Reading it left to right without decomposing it first is what makes long numerals look impenetrable; taking them one place value at a time makes them mechanical.

The limits of the system

Standard Roman numerals stop at 3,999 (MMMCMXCIX), because there is no symbol for 5,000 and M may not be repeated four times. The Romans handled larger values with a vinculum — a bar over a numeral multiplying it by a thousand — which is what the default mode above uses. There is also no zero and no way to write a fraction or a negative, which is precisely why positional decimal notation displaced the system for arithmetic while it survived for dates, monarchs and film credits.

Frequently Asked Questions

Why is 4 written IV and not IIII?

The subtractive form IV is the standard convention. IIII does appear historically and still survives on many clock faces, where it balances the VIII opposite it, but IV is what modern usage and this converter produce.

What is the largest Roman numeral?

In standard notation, 3,999 — written MMMCMXCIX. Beyond that a vinculum (an overline meaning × 1,000) is needed, which extends the range to 3,999,999.

Is IC a valid way to write 99?

No. Subtraction is only allowed in six specific pairs, and I may only precede V or X. The correct form is XCIX. This converter rejects IC as invalid rather than guessing.

Do Roman numerals have a zero?

No. There is no symbol for zero and no way to express negative numbers or fractions in the system, which is the main reason positional decimal notation replaced it for calculation.

Where these numbers come from

Sources

Official publications only. Links open the original document in a new tab.

National Institute of Standards and Technology Special Publication 811 — Guide for the use of the SI Significant figures and rounding conventions
National Institute of Standards and Technology CODATA fundamental physical constants Values of the fundamental physical constants

Roman Numeral Converter