Why is 4 written IV instead of IIII?

Standard Roman convention is subtractive: a smaller numeral before a larger one is subtracted (IV = 5−1 = 4). IIII appears on most clock faces by tradition (it's been used since at least the 14th century, possibly because it visually balances the VIII opposite it), but it's not standard for writing numbers anywhere else.

What's the largest number I can enter?

3,999 in standard Roman numerals (MMMCMXCIX). With the vinculum (overline) convention, you can go up to 3,999,999 — the bar over a numeral multiplies it by 1,000, so V̄ = 5,000 and M̄ = 1,000,000.

Why isn't 999 written IM?

Subtraction in Roman numerals is restricted: only I, X, and C can be subtracted, and only from the next two larger letters. So I can subtract from V or X (giving IV or IX), X from L or C (XL or XC), C from D or M (CD or CM). I→M would skip too many magnitudes. 999 is therefore CMXCIX (900 + 90 + 9), not IM.

How do I write 0 in Roman numerals?

There's no standard symbol for zero. The Romans simply wrote "nulla" (nothing) when they needed to express it in writing — but it never made it into the numeral system. If a tool insists you enter zero, it's not a true Roman numeral input.

Where do the overlines come from?

The vinculum (a horizontal bar above a letter) is a medieval-and-later notation that multiplies the letter by 1,000. So V̄ = 5,000, X̄ = 10,000, M̄ = 1,000,000. The Romans themselves used different conventions (sometimes parentheses); the overline version is what most modern references settled on.

Yes — but enter just the year part. Roman numerals don't have month or day notation in the standard system. To write a full date you'd typically use Roman numerals for the year and Arabic for month/day, or write them out in words.

Text & Writing Utilities · Free tool

Roman Numeral Converter

Convert numbers up to 3,999,999 to Roman numerals and back. Great for tattoos, chapters, and movie titles. Free, instant online converter with no sign-up.

Updated June 2026

Number → Roman

Roman numeral

MMXXVI

Roman → Number

Number

2026

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What it does

Convert Arabic numbers (1, 42, 2026) to Roman numerals (I, XLII, MMXXVI) and back, in either direction. Handles the standard 1–3,999 range that covers years, chapter numbers, monarch suffixes, Super Bowl numbering, and movie sequels — plus an extended mode using the overline (vinculum) convention to express numbers up to 3,999,999, where each overlined letter is multiplied by 1,000.

Common reasons people convert: writing the year on a tattoo or wedding invitation (2026 → MMXXVI), numbering chapters or outlines, reading clock faces that don't include digits, deciphering a movie sequel title (Rocky IV → 4), or spelling out a building's date stone or copyright year. The tool also flags common errors people make when writing Roman numerals — IIII for 4 (the clock-face exception, technically incorrect in standard usage), VL for 45 (should be XLV — V can't be subtracted), or chained subtractions like XIVX.

The conversion is a pure lookup: each Arabic digit maps to a Roman triad (units, tens, hundreds, thousands) using the subtractive forms IV, IX, XL, XC, CD, CM. Reverse parsing validates the input and rejects malformed numerals (you'll get an error, not a wrong answer).

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Example input & output

Input

Convert 2026 → Roman

Output

MMXXVI

Breakdown: MM (1000+1000) + XX (10+10) + VI (5+1) = 2026. The same year in 'MM' shows the rule that the same letter can repeat up to three times before subtraction kicks in.

How to use it

Enter a number (1 to 3,999,999) or a Roman numeral string in the input box.
The tool auto-detects the direction — typing digits converts to Roman, typing letters converts to Arabic.
If your input is over 3,999, the result uses overlines (rendered with HTML <span> for the macron). Copy the formatted output to keep the line.
Click Copy to put either format on your clipboard. Plain-text copy strips the overlines (since they don't survive paste into most apps).
Use the swap arrow to flip direction explicitly when both inputs would be ambiguous (e.g. "D" — is that 500 in Roman, or just the letter D?).

When to use this tool

Picking the right Roman numeral for a tattoo, wedding invitation, or anniversary plaque (year, date, ages).
Writing a chapter or outline numbering scheme that needs Roman numerals.
Cross-checking your Roman numeral homework, or sanity-checking a clock face.

When not to use it

Numbers above 3,999,999 — Roman numerals can't represent them in any standard convention.
Negative numbers, zero, or non-integers — Romans had no symbol for zero or fractions in the standard system.
Numerical sorting or arithmetic — Roman numerals aren't positional, so adding XLII + XCIX is much harder than 42 + 99.
Modern accounting or scientific notation — they're decorative, not computational.

Frequently asked questions

Why is 4 written IV instead of IIII?: Standard Roman convention is subtractive: a smaller numeral before a larger one is subtracted (IV = 5−1 = 4). IIII appears on most clock faces by tradition (it's been used since at least the 14th century, possibly because it visually balances the VIII opposite it), but it's not standard for writing numbers anywhere else.
What's the largest number I can enter?: 3,999 in standard Roman numerals (MMMCMXCIX). With the vinculum (overline) convention, you can go up to 3,999,999 — the bar over a numeral multiplies it by 1,000, so V̄ = 5,000 and M̄ = 1,000,000.
Why isn't 999 written IM?: Subtraction in Roman numerals is restricted: only I, X, and C can be subtracted, and only from the next two larger letters. So I can subtract from V or X (giving IV or IX), X from L or C (XL or XC), C from D or M (CD or CM). I→M would skip too many magnitudes. 999 is therefore CMXCIX (900 + 90 + 9), not IM.
How do I write 0 in Roman numerals?: There's no standard symbol for zero. The Romans simply wrote "nulla" (nothing) when they needed to express it in writing — but it never made it into the numeral system. If a tool insists you enter zero, it's not a true Roman numeral input.
Where do the overlines come from?: The vinculum (a horizontal bar above a letter) is a medieval-and-later notation that multiplies the letter by 1,000. So V̄ = 5,000, X̄ = 10,000, M̄ = 1,000,000. The Romans themselves used different conventions (sometimes parentheses); the overline version is what most modern references settled on.
Can I convert dates?: Yes — but enter just the year part. Roman numerals don't have month or day notation in the standard system. To write a full date you'd typically use Roman numerals for the year and Arabic for month/day, or write them out in words.

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