Roman Numeral Converter – Convert Numbers Online
Convert numbers to Roman numerals and Roman numerals back to numbers.
About the Roman Numeral Converter
What is the Roman Numeral Converter?
A Roman numeral converter turns a normal number into Roman numerals and decodes Roman numerals back into numbers.
Why use this calculator?
Roman numerals still appear on clock faces, building dates, film credits and chapter headings, so quick conversion is handy.
How to use it
- Choose the direction of conversion.
- Enter a number or a Roman numeral.
- Read the converted value.
Formula
Symbols are I=1, V=5, X=10, L=50, C=100, D=500 and M=1000; a smaller symbol before a larger one subtracts.
Standard Roman numerals cover 1 to 3,999; larger values use an overline in scholarly notation.
Frequently Asked Questions
What number is XL?
XL is 40, because X (10) before L (50) subtracts, giving 50 − 10.
Is there a Roman numeral for zero?
No. The classical Roman system had no symbol for zero.
How precise are the conversions?
Conversions use standard, internationally defined factors and are rounded for display. They are accurate to the number of digits shown.
Can I convert back and forth without losing accuracy?
Yes. Enter the original value to get an exact inverse conversion; avoid chaining rounded results if you need maximum precision.
Which measurement system is used?
Both metric (SI) and US customary / imperial units are supported and clearly labelled.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.
Does it work on a phone or tablet?
Yes. The layout is fully responsive, so it works on desktops, laptops, tablets and mobile phones, and every input adapts to touch screens.
Is the information I type kept private?
Yes. All calculations run locally in your browser. Nothing you enter is uploaded, stored or shared with anyone.