Roman Numeral Converter
Convert numbers to Roman numerals and back. Supports standard notation (I, V, X, L, C, D, M) plus vinculum (overbar) for values up to 3,999,999. Live conversion with step-by-step breakdown.
About this tool
Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500), M (1000) — combined additively and subtractively to represent positive integers. The system has no zero and no negatives, so it only handles values from 1 upward.
Example: 2026 becomes MMXXVI (1000+1000+10+10+5+1). Going the other way, MCMXCIV decodes to 1994. For values 4000 and above, the vinculum (overbar) multiplies a symbol by 1000 — V̄ = 5000, X̄ = 10000 — letting the tool reach up to 3,999,999.
Switch the tab to convert in either direction. A step-by-step breakdown shows how each symbol contributes to the total, which is helpful when checking whether a numeral on a building cornerstone, a movie copyright, or a numbered list is the one you expect.
FAQ
Why is 4 written as IV and not IIII? ›
The subtractive form IV (5 minus 1) is the canonical modern standard. The older additive IIII does appear on some clocks and inscriptions, but this tool follows the modern rules and flags IIII as non-standard when you convert it back.
What is the largest number I can convert? ›
3,999,999. Values from 4000 up use the vinculum (overbar) convention where a bar over a symbol multiplies it by 1000. Without the vinculum the classic limit is 3999 (MMMCMXCIX).
Did the Romans really use vinculum? ›
Yes — Roman inscriptions and medieval manuscripts used overbars (and other notations) to extend the system to large numbers. Modern popular usage rarely goes above 3999, but the convention is well-documented.
Do you have a tool that spells numbers as English words? ›
Yes — see the <a href="/tools/number-to-words/">Number to Words Converter</a> if you need cardinal (one, two, three), ordinal (first, second, third), or currency (dollars and cents) word forms for writing checks, invoices, or formal documents. That tool focuses on English word output, while this one focuses on the Roman numeral system.