Skip to content

CALCULATOR · Math

Roman Numeral Calculator

Convert Arabic numbers to Roman numerals (1–3999) and back, validate Roman syntax, and add or subtract two Roman numerals via integer arithmetic.

Show formula
Subtractive Roman numerals for integers 1–3999. Mapping: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Subtractive pairs: IV, IX, XL, XC, CD, CM. Addition / subtraction routed through integer arithmetic so the result is always canonical.

Inputs

Integer 1–3999.

Operands are parsed to integers, the operation runs in integer arithmetic, and the result is re-encoded in canonical Roman form. This sidesteps any need for "Roman-numeral algebra".

Result

Result

Result: MMXXVI

Arabic: 2026

Range
1–3999
Subtractive pairs
IV, IX, XL, XC, CD, CM
Show formula
Mappings I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Subtractive pairs IV, IX, XL, XC, CD, CM. Add / subtract go via integer arithmetic.

Supports integers 1–3999. The Romans had no standard form for zero, fractions, or large numbers (the vinculum convention came much later).

How the roman numeral calculation works

  1. Pick a mode — Arabic → Roman, Roman → Arabic, or addition / subtraction of two Roman numerals.
  2. Enter an integer (1–3999) or a Roman-numeral string in canonical subtractive form. Inputs outside the range or with non-canonical forms are rejected with a clear message.
  3. Read the canonical Roman numeral on the result panel. Arithmetic modes show each operand alongside the integer it represents.

Frequently asked questions

What is the supported range?

1 to 3,999. Romans did not have a standard form for zero, fractions or numbers above a few thousand (the overline / vinculum convention came later in medieval usage), so the calculator rejects anything outside that range.

Which Roman form does it produce?

Canonical subtractive form: IV not IIII, IX not VIIII, XL not XXXX. If your input uses the non-canonical form, the calculator will still parse it but the result is always the standard subtractive output.

Can it add or subtract Roman numerals?

Yes. Both operands are parsed to integers, the arithmetic runs, and the result is re-encoded in canonical Roman form. This is the safest path because it sidesteps all the rules of "Roman-numeral algebra" (which never existed).

Examples

Convert 2026.
The output is MMXXVI, broken down as 2×1000 + 2×10 + 5 + 1.
XIV + XII.
The sum is XXVI, because 14 + 12 = 26.

Related calculators