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Roman Numeral Converter

Convert between Arabic numbers and Roman numerals

⇄
Roman numeral reference
I1
V5
X10
L50
C100
D500
M1000
V̄5000
X̄10000

How Roman numerals work

  • The seven base letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000
  • Additive rule: place larger then smaller (VI = 6, MCC = 1200)
  • Subtractive rule: place smaller before larger to subtract (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900)
  • The same letter cannot appear more than 3 times in a row (so 4 is IV, not IIII)
  • For numbers above 3,999 a bar (vinculum) over a letter multiplies it by 1000 — this tool uses V̄, X̄, L̄, C̄, D̄, M̄

Common use cases

  • Movie credits and copyright years (©MMXXIV)
  • Book chapters and outlines
  • Clock faces and watch designs
  • School assignments and history homework

User Reviews

Average 4.8 stars based on 6 user reviews.

Ryan Liu2026-05-06
Role: Operator

I found Roman Numeral Converter while looking for free online roman numeral converter, and the real issue was that checking units and values across sources is slow. Number to Roman and roman to number are on the same page, so I can quickly check whether the result looks right without stitching several tools together.

Steven Sun2026-02-11
Role: Student

For roman numeral converter work, the important part is whether the output is easy to verify. Roman Numeral Converter puts roman to number up front, it saves time for teaching, office, and daily calculations, and it handles arabic to roman work without sending me to another page.

Henry He2026-05-16
Role: Freelancer

Our team runs into this during quick office calculation: quick conversions are easy to calculate with the wrong formula. Roman Numeral Converter keeps the roman numeral converter flow short, and reference chart helps with pre-handoff review for repeated Freelancer work.

Nathan Ma2026-02-21
Role: Project Member

I needed roman numeral converter that could quickly check whether the result looks right, not just a generic page. Roman Numeral Converter keeps reference chart and number (1 to 3,999,999) close to the real workflow, and it reduces manual conversion and repeated input.

Frank Xu2026-05-26
Role: Data Clerk

For people searching free online roman numeral converter, this page matches the intent well. It is not a generic utility; Roman Numeral Converter is built around arabic to roman; it is less error-prone than applying a formula manually, and the result is easy to keep working with.

Lisa Li2026-02-05
Role: Everyday User

During Book chapters and outlines, Roman Numeral Converter solves the part I worry about most: quick conversions are easy to calculate with the wrong formula. By keeping roman numeral visible in the workflow, there is less manual cleanup, and it gives a result that is easy to review, so it belongs in my regular tool list.