What's the subtractive rule?

When a smaller numeral appears immediately before a larger one, you subtract: IV = 5 − 1 = 4, IX = 10 − 1 = 9, XL = 50 − 10 = 40. Only six pairs are valid: IV, IX, XL, XC, CD, CM. Anything else like IL or IC is wrong.

Why isn't 4 written as IIII?

Because the standard form is subtractive — IV. IIII does appear on traditional clock faces (a typographic choice for visual balance with VIII on the opposite side), but it's non-standard for everything else.

3,999,999. Beyond that the system breaks down: there's no widely-agreed symbol for ten million. We use parenthesised groups for ×1000 multipliers, which is the modern ASCII equivalent of the classical vinculum (overline). So 5,000 is (V), 10,000 is (X), etc.

No. Romans had no symbol for zero — the concept arrived in Europe with the Hindu-Arabic numeral system in the 12th-13th century. Medieval clerks who needed it sometimes wrote 'N' (for the Latin 'nullus'), but it isn't standard.

Why are clock faces sometimes IIII instead of IV?

Tradition. The earliest mechanical clocks used IIII as a visual counter-weight to VIII on the opposite side of the dial — IV looks too light next to VIII. Many modern luxury watchmakers preserve this convention; it's not a 'mistake'.

What about V̄ or X̄ with an overline?

Classical Latin used a vinculum (overline) to multiply by 1,000 — so V̄ meant 5,000. Modern ASCII can't show the overline reliably, so we render it as (V). Both mean the same thing.

Are negative Roman numerals possible?

Not historically. The system has no sign. The calculator rejects negative input rather than invent a convention.

Roman Numeral Converter

1994 ↔ MCMXCIV — in both directions, with full validation.

Roman numerals trace back to 5th-century BC Etruria and stayed the European standard for two thousand years before Arabic numerals displaced them in the 13th century. They’re still everywhere: chapter numbers, regnal names, copyright dates on old films, Super Bowl branding. The converter below handles standard subtractive form (IV = 4, IX = 9) with strict validation — common mistakes like ‘IIII’ or ‘VV’ are flagged as invalid rather than silently parsed.

Number

Roman

MCMXCIV

Standard subtractive form (IV = 4, IX = 9, XL = 40, XC = 90). Numbers ≥ 4,000 use parenthesised thousands — the ASCII-safe rendering of the classical vinculum (overline).

How to use

Pick a direction
Arabic → Roman if you have a number; Roman → Arabic if you have a numeral and want to know what year that film was made.
Type the value
Numbers up to 3,999,999. Letters I V X L C D M (and parentheses for ×1000 groups). The converter is case-insensitive on input but always emits uppercase.
Copy or swap
Use the copy button for the result. The swap button flips the direction and feeds the output back as input — useful for round-tripping.

Common conversions

Arabic	Roman	Reads as
1	I	one
4	IV	four (one before five)
9	IX	nine
40	XL	forty
90	XC	ninety
400	CD	four hundred
900	CM	nine hundred
1492	MCDXCII	Columbus year
1969	MCMLXIX	Apollo 11
1994	MCMXCIV	most-asked example
2026	MMXXVI	current year
3999	MMMCMXCIX	last ‘normal’ value
5000	(V)	parenthesised thousands

Frequently asked questions

What's the subtractive rule?: When a smaller numeral appears immediately before a larger one, you subtract: IV = 5 − 1 = 4, IX = 10 − 1 = 9, XL = 50 − 10 = 40. Only six pairs are valid: IV, IX, XL, XC, CD, CM. Anything else like IL or IC is wrong.
Why isn't 4 written as IIII?: Because the standard form is subtractive — IV. IIII does appear on traditional clock faces (a typographic choice for visual balance with VIII on the opposite side), but it's non-standard for everything else.
What's the maximum?: 3,999,999. Beyond that the system breaks down: there's no widely-agreed symbol for ten million. We use parenthesised groups for ×1000 multipliers, which is the modern ASCII equivalent of the classical vinculum (overline). So 5,000 is (V), 10,000 is (X), etc.
Is there a zero?: No. Romans had no symbol for zero — the concept arrived in Europe with the Hindu-Arabic numeral system in the 12th-13th century. Medieval clerks who needed it sometimes wrote 'N' (for the Latin 'nullus'), but it isn't standard.
Why are clock faces sometimes IIII instead of IV?: Tradition. The earliest mechanical clocks used IIII as a visual counter-weight to VIII on the opposite side of the dial — IV looks too light next to VIII. Many modern luxury watchmakers preserve this convention; it's not a 'mistake'.
What about V̄ or X̄ with an overline?: Classical Latin used a vinculum (overline) to multiply by 1,000 — so V̄ meant 5,000. Modern ASCII can't show the overline reliably, so we render it as (V). Both mean the same thing.
Are negative Roman numerals possible?: Not historically. The system has no sign. The calculator rejects negative input rather than invent a convention.

About

Where you still see them

Regnal names (Queen Elizabeth II), chapter numbers in formal books, monumental inscriptions, copyright dates on classic films and TV (often hidden in the credits), Super Bowls, World Wars (WWII), watch faces, music theory (figured bass uses Roman degree numerals), and outlines (I, II, III, IV instead of 1, 2, 3, 4).

Why they fell out of arithmetic use

There's no positional value — the symbol's worth depends on what's next to it, not where it sits — so adding XXVII to LXVIII is a slog where 27 + 68 isn't. Hindu-Arabic numerals replaced Roman in European arithmetic between the 13th and 16th centuries, kept around afterwards only for naming and ornament.