Roman Numeral Calculator
Convert numbers between decimal and Roman numerals, and perform basic operations with Roman inputs.
Decimal → Roman
Roman → Decimal
Roman Arithmetic
What is a calculadora romana?
A calculadora romana is a tool that works with Roman numerals instead of standard Arabic numbers. It helps you convert values like 42 into XLII, decode Roman numerals like MCMXCIX, and even perform calculations using Roman notation.
This is especially useful for students, teachers, puzzle enthusiasts, and anyone working with historical dates, book chapters, clock faces, or inscriptions.
How to use this Roman numeral calculator
1) Convert decimal to Roman
Type a whole number from 1 to 3999 and click Convert to Roman. The calculator instantly returns the correct Roman numeral.
2) Convert Roman to decimal
Type a Roman numeral such as XIV or MMXXVI and click Convert to Decimal. The tool validates the format and gives you the numeric value.
3) Perform Roman arithmetic
Enter two Roman numerals, choose an operator (+, −, ×, ÷), and click Calculate. You will see the decimal result and, when possible, the Roman result too.
Roman numeral rules you should know
- I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000
- Symbols are usually written from largest to smallest: VIII = 8.
- A smaller symbol before a larger one means subtraction: IV = 4, IX = 9, XL = 40, CM = 900.
- Not every combination is valid. For example, IIII is not the standard form for 4; IV is.
Quick examples
- 2026 → MMXXVI
- XLIV → 44
- X + V → 15 (XV)
- C − X → 90 (XC)
Limits and best practices
This calculator follows the most common modern Roman numeral standard and supports values from 1 to 3999 for Roman output. Results outside this range, non-integers, or non-positive outcomes are shown in decimal only.
If you are learning Roman numerals, this is a fast way to check homework and build confidence. If you are building educational content, it is a handy reference for accurate conversions.