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Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals back to numbers, instantly. Subtraction rule, invalid-sequence detection, date & century mode, large numbers with vinculum, and a step-by-step breakdown — all free.

Quick answerA Roman numeral converter changes numbers (1–3999) into I, V, X, L, C, D, M symbols, and converts Roman numerals back into numbers. The subtraction rule (IV=4, IX=9, XL=40) is applied automatically, and invalid sequences are flagged. For example, 2026 = MMXXVI. Turn on vinculum mode to write numbers up to 3,999,999.
Range: 1 – 3999 With vinculum, up to 3,999,999 2026 = MMXXVI Updated: Jul 19, 2026
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Enter a number from 1 to 3999. Up to 3,999,999 with vinculum mode on.
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Only the letters I, V, X, L, C, D, M. Use an underscore for vinculum: _V = V̅ (5000).
Write a date in Roman numerals (day · month · year):
US-style order swaps day and month, e.g. July 19, 2026 reads VII·XIX·MMXXVI.
Pick a style below or compare all styles at once in the result panel — handy for choosing a tattoo or engraving layout.
Find which century a year belongs to, in Roman numerals:
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E.g. 2026 → 21st century (XXI). Enter a year from 1 to 3999.
⚙️ Advanced — vinculum (large numbers), lowercase, clock format
Vinculum (overline) modeFor numbers larger than 3999 (V̅ = 5000). Up to 3,999,999.
Lowercase outputShow the Roman numeral in lowercase (mmxxvi).
Clock format (IIII)Use the clock-face tradition IIII for 4 instead of IV.
MMXXVI2026 (this year)
I V X L C D M7 basic symbols
1 – 3999Standard range
MMMCMXCIXLargest standard number (3999)
⚙️ How it works: This tool runs entirely in your browser using a precise algorithm — no data is sent to a server. Number → Roman conversion maps place values from largest to smallest; Roman → Number conversion reads left to right and validates the result with a round-trip check. This catches invalid sequences like IIII, VV, or IC and suggests the correct form. The standard system covers 1–3999; vinculum mode extends that to 3,999,999.
🏛️ Roman Numeral Converter — ToolPico ↗

What are Roman numerals, and how do you convert them?

A complete guide to the Roman numeral system, its writing rules, the subtraction logic, and step-by-step number ↔ Roman conversion.

Roman numerals are a number-writing system developed in ancient Rome that uses just seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Every number is built by arranging these symbols according to a small set of rules. Converting Roman numerals means turning an ordinary number (1, 2, 3…) into these symbols, or reading Roman symbols back into a number. Today Roman numerals still show up on clock faces, in book chapters and outlines, in movie sequel titles, in the names of monarchs and popes, on building cornerstones, and — a very American example — in Super Bowl names like Super Bowl LVIII.

What are the rules for writing Roman numerals?

Quick answerFive core rules: (1) Symbols are arranged from largest to smallest, left to right, and their values are added (XVI = 16). (2) I, X, and C can repeat up to three times; V, L, and D never repeat. (3) Subtraction is only used for the pairs IV, IX, XL, XC, CD, CM. (4) A subtracting symbol is used only once (IIX is invalid; the correct form is VIII). (5) The standard range is 1–3999.
  • Addition: Smaller symbols to the right of a larger one are added on. LXVII = 50+10+5+1+1 = 67.
  • Subtraction: A smaller symbol placed before a larger one is subtracted. IV = 5−1 = 4, CM = 1000−100 = 900.
  • Repetition limit: The same symbol appears at most three times in a row (III = 3, but 4 is IV, never IIII, in standard notation).
  • No zero: The Roman system has no symbol for zero; it starts at 1.

How do you convert a number to a Roman numeral? (step by step)

Quick answerSplit the number into place values, write each one starting from the largest matching symbol, then combine them. Example 2026: thousands 2000 = MM, hundreds 0 = (none), tens 20 = XX, ones 6 = VI → MMXXVI. The tool above shows this breakdown automatically for every conversion.

On the "Number → Roman" tab, every number you enter produces a step-by-step breakdown: you'll see which symbol was used how many times, and how much each step contributes to the total. You don't just get the answer — you can see exactly how the conversion works.

How do you convert a Roman numeral to a number?

Quick answerRead the symbols left to right: if a symbol is smaller than the one to its right, it's subtracted; otherwise it's added. MMXXVI: M+M+X+X+V+I = 1000+1000+10+10+5+1 = 2026. The tool also checks whether the sequence is valid, and suggests the correct spelling if it isn't.

Numbers larger than 3999: the vinculum (overline)

Quick answerThe standard system ends at MMMCMXCIX = 3999. Larger numbers use a line (vinculum) placed over a symbol, which multiplies its value by 1000: V̅ = 5000, X̅ = 10,000, M̅ = 1,000,000. Turn on "Advanced → Vinculum mode" to convert numbers up to 3,999,999; when typing, use the underscore shortcut (_V = V̅).

Common number-to-Roman-numeral conversions

The most frequently looked-up numbers and years, with their Roman numeral equivalents. Use the converter above for any number of your own.

Popular numbers and years converted to Roman numerals
NumberRoman numeralNote
4IVSubtraction rule (5−1)
9IXSubtraction rule (10−1)
14XIV10 + 4
40XL50−10
90XC100−10
500DBasic symbol
1,776MDCCLXXVIDeclaration of Independence
2,026MMXXVIThis year (21st century)
3,999MMMCMXCIXLargest standard number

Quick links

Related tools: clock face, list & Roman arithmetic

Visualize Roman numerals, generate a bulk list, and add or subtract two Roman numerals — all in your browser.

🕓Roman numeral clock face
Draws a 12-hour clock face using Roman numerals. Choose IV or the traditional clock-face IIII for 4.
📋Range list generator
Generates the Roman numeral for every number in a range at once (up to 200 rows).
➕Roman numeral arithmetic
Add or subtract two Roman numerals; the result is given back as a Roman numeral.

Roman numeral reference tables

Quick-lookup charts for ones, tens, hundreds, years, and large numbers with the vinculum.

Roman numerals from 1 to 10
NumberRomanNumberRoman
Tens: 10, 20, 30 … 100
NumberRomanNumberRoman
Hundreds: 100, 200, 300 … 1000
NumberRomanNumberRoman
Notable years
YearRoman numeralNote
1776MDCCLXXVIDeclaration of Independence
1969MCMLXIXMoon landing
2000MMMillennium
2024MMXXIV—
2025MMXXV—
2026MMXXVIThis year
Large numbers with the vinculum (overline) — a line multiplies the value by ×1000
NumberOverlinedNote
4,000I̅V̅4 × 1000
5,000V̅5 × 1000
10,000X̅10 × 1000
50,000L̅50 × 1000
100,000C̅100 × 1000
1,000,000M̅1000 × 1000

Note: the overline may render as a small line above or to the upper-right of the letter depending on your font. To use this mode in the converter, turn on "Advanced → Vinculum mode."

Add this converter to your site (embed code)

Embed the Roman numeral converter on your own website for free. Copy the code below into your HTML — the tool runs in a simplified view and links back to this page as its source.

The embedded tool has a fixed layout; you can adjust the height value to fit your site. No ads or personal data, runs entirely client-side.

Roman numeral glossary

Short definitions of the terms used throughout this guide.

Basic symbolThe 7 letters of the Roman system: I, V, X, L, C, D, M. Each has a fixed value.
Subtraction ruleA smaller symbol placed before a larger one is subtracted: IV=4, IX=9, CM=900.
Addition ruleSymbols arranged from largest to smallest have their values added: DCLXVI=666.
Vinculum (overline)A line placed over a symbol multiplies its value by 1000: V̅=5000. Used for numbers above 3999.
Repetition limitI, X, C can repeat up to 3 times; V, L, D never repeat.
Absence of zeroRoman numerals have no symbol for zero; the system starts at 1.
Century notationA year's century is written in Roman numerals: 2026 → XXIst century.
Clock format (IIII)Traditional clocks often show IIII for 4 instead of the mathematical IV.

In-depth guides

Detailed answers to the most common Roman numeral questions.

Why is 4 written IV, but IIII on clocks?

Mathematically, the correct Roman spelling of 4 is IV (subtraction rule: 5−1). Yet many traditional clock faces show 4 as IIII instead. Several explanations are offered: visual symmetry with VIII on the opposite side of the dial, easier readability at a glance (so IV and VI aren't confused), and long-standing clockmaking tradition.

You can draw both versions with the "Roman numeral clock face" tool above and compare them yourself. In the converter, the "Advanced → Clock format (IIII)" toggle lets you switch how 4 is written.

How do you write numbers larger than 3999? (vinculum guide)

Because the standard system tops out at M (1000), the largest number it can express is MMMCMXCIX = 3999. For larger numbers, the Romans used a vinculum — an overline that multiplies a symbol's value by 1000. So V̅ = 5000, X̅ = 10,000, and M̅ = 1,000,000.

Turn on "Advanced → Vinculum mode" in this tool to convert numbers up to 3,999,999. To type a vinculum in the "Roman → Number" field, use the underscore shortcut: _V means V̅ (5000).

Which Roman numeral sequences are invalid?

Most mistakes break either the repetition rule or the subtraction rule. For example, IIII for 4 (correct: IV), IM for 999 (correct: CMXCIX), and IL for 49 (correct: XLIX) are all invalid. In subtraction, I can only be subtracted from V and X; X only from L and C; and C only from D and M.

This tool checks whatever you type in "Roman → Number" mode with a round-trip validation: it first works out the numeric value, then converts that value back into a Roman numeral and compares the two. If they don't match, it flags the sequence as invalid and suggests the correct spelling.

Roman numeral tattoo & keepsake ideas

Roman numeral dates are one of the most popular tattoo and keepsake formats — a wedding date, a birthday, an anniversary, or a birth date rendered as a compact string of letters like XIX·VII·MMXXVI. Because the numerals themselves don't change, the real design decision is the separator and layout: how the day, month, and year are divided, and whether they run horizontally or stack vertically.

Common separator conventions, from most to least traditional:

  • Dot ( · ) — the most common choice for engravings and tattoos; reads as a clean, classical punctuation mark between day, month, and year.
  • Slash ( / ) — mirrors a familiar numeric date format (DD/MM/YYYY), making the Roman version easier for others to parse at a glance.
  • Dash ( – ) — a slightly bolder, more modern look; works well in sans-serif or block-letter tattoo lettering.
  • Space — minimalist, no punctuation at all; lets the numeral groups themselves create the visual separation.
  • Stacked vertical — day, month, and year on three separate lines instead of one row; a natural fit for a vertical placement such as a forearm, spine, or ribcage, or for a small pendant or ring engraving.

To try these out, switch to the Date mode above, enter the day, month, and year, and use the Separator style picker — the result panel shows a live preview in your chosen style, plus a row of preview cards for all five styles at once with a one-click Copy button on each, so you can compare options before committing to ink or an engraving.

This is a general style guide, not tattoo or medical advice. Always double-check the exact spelling with a professional before any permanent placement, and be aware that fonts and artists may render the overline (vinculum) or serif details differently.

Frequently asked questions

How do you write Roman numerals?
Roman numerals use seven basic symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Symbols are arranged largest to smallest, left to right, and their values are added (XVI = 16). The same symbol repeats at most three times. For 4, 9, 40, 90, 400, and 900, the subtraction rule applies: a smaller symbol placed before a larger one is subtracted (IV=4, CM=900).
How do you write 4 in Roman numerals?
The number 4 is written as IV: I (1) is placed before V (5), meaning 5−1 = 4. Writing IIII is mathematically incorrect; it's used only by tradition, mainly on clock faces, for the number 4.
How do you write 2026 in Roman numerals?
The number 2026 is written as MMXXVI. Breakdown: MM=2000, XX=20, VI=6; total 2000+20+6 = 2026. As a year, MMXXVI falls in the 21st century (XXI).
How do you convert numbers to Roman numerals?
Going from a number to Roman numerals, split the number into place values and write each with the matching symbols (MMXXVI). Going the other way, read the symbols left to right; a smaller symbol before a larger one is subtracted, otherwise it's added. Just type the number or the Roman numeral into the tool above — the direction is detected automatically.
What are the rules for writing Roman numerals?
(1) Symbols are arranged from largest to smallest and added together. (2) I, X, C repeat at most three times; V, L, D never repeat. (3) Subtraction only applies to the pairs IV, IX, XL, XC, CD, CM. (4) A subtracting symbol is used only once (IIX is invalid, the correct form is VIII). (5) The standard system covers 1–3999.
What does M mean in Roman numerals?
M represents 1000. MM = 2000, MMM = 3000. M is the largest single symbol in the standard system; for 4000 and above, a line (vinculum) is placed over a symbol to multiply its value by 1000.
Can numbers larger than 3999 be written in Roman numerals?
The standard system covers 1–3999. Larger numbers use the "vinculum" (overline) method: a line over a symbol multiplies its value by 1000 (V̅=5000, X̅=10,000, M̅=1,000,000). Turn on "Vinculum mode" in this tool to convert numbers up to 3,999,999.
Why is 4 written as IIII on clocks?
Many traditional clock faces show 4 as IIII instead of IV. Reasons commonly cited include visual symmetry with VIII on the opposite side of the dial, readability, and historical clockmaking tradition. The mathematically correct spelling is IV; IIII is a convention specific to clock faces.
What's the best way to write a Roman numeral date for a tattoo?
There's no single "correct" separator — it comes down to style and placement. The most common conventions are a dot (X·VII·MMXXVI), a slash (X/VII/MMXXVI), a dash (X–VII–MMXXVI), a plain space, or a stacked layout with day, month, and year on three separate lines — a good fit for a vertical placement like a forearm or spine. Use the Date mode above to preview all five styles side by side and copy the exact spelling before booking an appointment or ordering an engraving.

Methodology & sources

ToolPico's Roman Numeral Converter is a free, independent tool. The conversion engine uses a precise, deterministic algorithm: Number → Roman conversion maps values from largest to smallest using the standard symbol table (M, CM, D, CD, C, XC, L, XL, X, IX, V, IV, I); Roman → Number conversion reads the sequence left to right, then validates it by converting the result back into a Roman numeral and comparing (round-trip validation). This method reliably catches non-standard sequences such as IIII, VV, or IC.

Basis: Standard (classical) Roman numeral rules; the vinculum (overline) extension is supported up to 3,999,999. Calculations run entirely client-side (in your browser); no data is sent to a server. Last updated: July 19, 2026.
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