How to Read Roman Numerals: Addition and Subtraction

Seven symbols and a consistent convention

The standard symbols are I=1, V=5, X=10, L=50, C=100, D=500 and M=1000. In common modern subtractive notation, IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900.

This dictionary uses that modern convention for integers from 1 through 3,000. Historical inscriptions and some clock faces use different forms, such as IIII for four. A difference in historical notation does not change the underlying quantity.

Build by place-value chunks

Forty-nine is 40 + 9, so it is XLIX. It is not IL: standard subtractive notation does not allow I to be placed before L to subtract 1 from 50. Four hundred forty-four is 400 + 40 + 4, giving CDXLIV.

For 2026, write 2000 + 20 + 6: MM + XX + VI = MMXXVI. The same approach works across the dictionary: handle thousands, hundreds, tens and units in that order.

Roman notation is not a positional base

Unlike decimal or binary, Roman numerals do not use a zero placeholder to assign place value. The order and permitted symbol combinations carry the structure. Do not apply binary conversion rules to a Roman string.

To check an answer, split it into familiar additive and subtractive groups, then total their values. The number dictionary pairs each Roman result with its decimal and English forms so the intended value remains clear.

Check the mathematical definitions

For fractions, percentages and worked arithmetic, see OpenStax Prealgebra. For number definitions, see OpenStax on prime and composite numbers and Wolfram MathWorld on digital roots. Worked examples on this page are calculated for this guide.