Roman Numeral Converter

Convert between Arabic numbers and Roman numerals. Standard notation handles 1-3999; vinculum notation (overlines for ×1000) extends to 3,999,999. Live two-way binding.

How to use the Roman Numeral Converter

Type a number, see the Roman numeral. Type Roman numerals, see the number. Vinculum (overline = multiply by 1000) is used in output above 3999 — represented here with parentheses: (IV) means 4000.

Standard and vinculum Roman numerals

Roman numerals build values from seven letters — I, V, X, L, C, D, M — added left to right, with a smaller letter before a larger one signalling subtraction (IV is 4, CM is 900). In standard form that reaches 3999, because there is no single symbol for 5000 and you would otherwise need a run of M characters beyond it. This converter binds the two directions live: type a number to see the numeral, or type a numeral to see the number.

To go higher it uses the vinculum — a bar over a numeral that multiplies it by 1000 — shown here with parentheses, so (IV) is 4000 and the tool extends to 3,999,999. If you only need to render a year for a copyright line or a cornerstone, the date to Roman numerals tool is tuned for that; this one is the general-purpose number converter.

Common use cases

• Large numbers — convert values above 3999 using vinculum notation the basic form cannot express.
• Decoding inscriptions — read a numeral from a monument, book, or clock face back to a number.
• Outlines and numbering — produce numerals for sections, appendices, or list items.
• Design and typography — get an accurate numeral string before setting it in a layout.
• Teaching the system — show how subtractive pairs and the vinculum work by editing either field.