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Roman Numerals to Decimal
Tool Description
Roman Numerals to Decimal is a free online Roman-Decimal converter with two-way conversion and validity check. It runs entirely in your local browser, no upload required, no installation needed, ideal for quick conversion in history, clocks, and film contexts.
How to Use
- Enter Content
Enter Roman numerals or decimal values in the input box, one per line, supports batch.
- Choose Conversion
Click Roman to Decimal or Decimal to Roman to convert, or click Verify Validity to check Roman numerals.
- Export Result
Click Copy Result or Download Result to save content.
Use Cases
- Historical Dating: Convert Roman year numbers in books and inscriptions to Arabic for clarity
- Clocks & Film: Decode Roman numerals on clock faces and movie credits
- Teaching & Learning: Help students master Roman-Decimal mapping
Key Advantages
- Free to Use
The tool is completely free, no registration or login required.
- Privacy Safe
All processing happens in your local browser; content is never uploaded.
- Two-way Conversion
Both Roman-to-Decimal and Decimal-to-Roman are supported, plus validity check.
- Batch Processing
Process multiple lines at once for higher efficiency.
- Instant & Accurate
Local computation responds instantly, following Roman numeral rules.
- Easy to Use
Clear interface, no learning curve, ready to use instantly.
Roman Numeral Basics
Roman numerals use seven basic symbols combined by "subtract left, add right" rule. Mapping below.
| Symbol | Value | Note |
|---|---|---|
| I | 1 | Smallest basic unit |
| V | 5 | Group of five |
| X | 10 | Multiple of ten |
| L | 50 | Fifty |
| C | 100 | Multiple of hundred |
| D | 500 | Five hundred |
| M | 1000 | Multiple of thousand, largest single symbol |
Tips
Decimal to Roman supports 1-3999; out-of-range inputs show an error.
In Roman numerals the same symbol repeats at most three times (e.g. III); subtract pairs are limited to IV, IX, XL, XC, CD, CM.
Frequently Asked Questions
Roman-Decimal converter converts bidirectionally between Roman and Arabic numerals and checks Roman validity.
Enter content in the input box, click Roman to Decimal or Decimal to Roman to convert.
It supports standard Roman numerals (I-X combinations) and decimals 1-3999, one per line for batch.
The standard Roman range is 1 to 3999; out-of-range inputs show an error.
Computation is local, instant response, results appear on click.
Safe. All conversion runs locally; content is never uploaded.
We provide free daily uses so light daily needs cost nothing; for higher limits, a membership unlocks more.
Yes. The page is responsive for phones, tablets, and computers.
No installation, ready instantly, and it supports validity check to catch bad input early.
Common causes: repeated disallowed symbols like VV or LL, or more than three identical symbols in a row; use Verify to locate the problem line.
The tool strictly follows Roman rules, accurate and reliable; invalid inputs are flagged and skipped.
Yes. Enter one item per line for batch conversion, results output line by line.
Content last updated：2026-07-10
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