Roman numeral calculator.

Worked example

XIV + IX: XIV is 14 and IX is 9, so the sum is 23, which is XXIII. XVII ÷ V: 17 divided by 5 is 3 remainder 2, so the quotient is III with a remainder of II. V − V has no answer because Roman numerals have no zero symbol.

How it works

Each numeral is converted to its number, the arithmetic is done on ordinary integers, and the result is written back in standard form. Older additive forms such as IIII are accepted as input and the answer is always given in standard subtractive form.

The Roman system has no zero symbol, and this tool does not invent a notation for negatives, so a result of 0 or less is reported as impossible. Division gives a whole-number quotient and shows the remainder, since there are no fractions.

Standard numerals stop at 3,999 (MMMCMXCIX). When an answer is larger, the tool still shows the number but says it has no standard Roman form.

Sources and basis (opened 2026-10-15): Roman numerals - Wikipedia (letter values, subtractive notation, additive forms, the 3,999 maximum and the absence of a zero).

FAQ

How do you add Roman numerals?

Convert each to a number, add them, and convert the sum back. XIV + IX = 14 + 9 = 23 = XXIII.

Can Roman numerals show zero or negative numbers?

There is no Roman zero symbol, and this tool does not invent a notation for negatives. A result of zero or below is reported as impossible.

What happens when the answer is over 3999?

The number is shown, but there is no standard Roman numeral for it. Larger numbers need extra notation such as a bar over the letters.

How does division work?

Roman numerals have no fractions, so you get a whole quotient and a remainder: XVII divided by V is III remainder II.

Does it accept IIII for 4?

Yes. Additive forms like IIII are read, and the answer is written in standard form.