Roman Numeral Converter - Numbers to Roman and Back
Convert numbers to Roman numerals and Roman numerals back to numbers instantly — bidirectional, with strict validation and one-click copy.
Tool Interface
| Symbol | I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|---|
| Value | 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
How to use
- Pick a direction: Number to Roman, or Roman to Number.
- Type a whole number from 1 to 3999, or a Roman numeral such as MMXXVI.
- Press Convert (or Enter) to see the result instantly, then Copy result if you need it.
- Everything runs in your browser — no signup, nothing uploaded.
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About This Tool
Introduction: Convert Roman Numerals Both Ways
Roman numerals show up everywhere — clock faces, book chapters, movie sequels, Super Bowl numbers, and historical dates. Trencada's free Roman Numeral Converter works in both directions: turn any whole number from 1 to 3999 into its Roman numeral, or paste a Roman numeral to decode it back to a number. Every conversion is validated strictly, so malformed numerals like IIII or IC are rejected with a clear explanation instead of a wrong answer.
How to Use the Roman Numeral Converter
- Pick a direction: Number to Roman, or Roman to Number.
- Type your value: a whole number from 1 to 3999, or a Roman numeral such as MMXXVI.
- Press Convert (or hit Enter) — the result appears instantly.
- Copy result with one click to paste it anywhere.
Key Features
- Bidirectional: numbers to Roman numerals and Roman numerals to numbers
- Strict validation: rejects invalid forms like IIII, VV, or IC
- Full range: every number from 1 (I) to 3999 (MMMCMXCIX)
- One-click copy of every result
- Symbol reference table built into the page (I, V, X, L, C, D, M)
- 100% private: runs entirely in your browser, nothing uploaded
Why Choose Trencada
Every Trencada tool is free forever with no accounts, no installation, and no hidden costs. The Roman Numeral Converter runs 100% in your browser — your conversions never leave your device.
Frequently Asked Questions
What is the largest number I can convert?
3999 (MMMCMXCIX). Standard Roman numerals do not go higher without special overline notation, so the converter caps at 3999.
Why was my Roman numeral rejected?
The converter enforces strict Roman numeral rules: symbols cannot repeat more than three times (IIII is invalid — use IV), and only I, X, and C can be used subtractively (IC is invalid — use XCIX for 99).
How do Roman numerals work?
Seven symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. A smaller symbol before a larger one subtracts (IV=4, IX=9, XL=40). The reference table on the page shows all seven.
Is my input private?
Yes. The tool runs entirely in your browser — nothing you type is uploaded or stored anywhere.