Roman numeral converter and canonical form checker
Choose a direction and enter a decimal integer or Roman numeral. HitEquals converts it, shows the symbol breakdown and rejects noncanonical forms such as IIII or IC.
Inputs used by this calculator
Roman Numeral Converter uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Conversion | Decimal to Roman | Decimal to Roman · Roman to decimal | Supplies the conversion quantity used by the published equation or result breakdown. |
| Decimal integer | 1,994 | 1 to 3999 | Supplies the decimal integer quantity used by the published equation or result breakdown. |
| Roman numeral | MCMXCIV | Text in the format shown | Supplies the roman numeral quantity used by the published equation or result breakdown. |
Roman numeral symbols
Seven Latin letters carry the common values I, V, X, L, C, D and M. Values usually descend and are added.
Subtractive pairs
Six standard pairs place a smaller value before a larger one: IV, IX, XL, XC, CD and CM. The converter emits only canonical modern forms.
Convert decimal to Roman
Take the largest available symbol or pair repeatedly and subtract its value until the remainder is zero.
Convert Roman to decimal
Read recognized tokens from left to right and add their values. The result is converted back to Roman to ensure the input was canonical.
Range and typography
This tool supports 1–3,999 using ordinary Latin letters. Unicode recommends composing Roman numerals from Latin letters for most purposes; larger historical forms require separate conventions.
What the Roman Numeral Converter answers
Convert standard Roman numerals and decimal integers from 1 through 3,999.
Use Roman Numeral Converter when you know Conversion, Decimal integer and Roman numeral and need the relationship expressed by the published equation.
Roman numeral values
| Token | Value | Token | Value |
|---|---|---|---|
| M | 1000 | CM | 900 |
| D | 500 | CD | 400 |
| C | 100 | XC | 90 |
| L | 50 | XL | 40 |
| X | 10 | IX | 9 |
| V | 5 | IV | 4 |
| I | 1 | — | — |
Frequently asked questions
What does MCMXCIV equal?
It equals 1,994.
Why is 4 written IV?
I before V subtracts one from five.
Is IIII accepted?
This converter requires the common canonical form IV.
Can Roman numerals represent zero?
The classical system used here has no zero symbol.
Why is the maximum 3,999?
Values above it need repeated M or an extended convention such as overbars, which is not universal.
What question does this Roman Numeral Converter answer?
Convert standard Roman numerals and decimal integers from 1 through 3,999.
What to keep in mind
Uses the common modern canonical form for 1–3,999. Historical conventions and overbar notation vary.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.