Roman Numeral Converter

Read the Roman letters as groups, not isolated marks

Roman numerals are built from I, V, X, L, C, D and M. The seven Roman letters carry fixed values rather than place values, so XX means 10 + 10 instead of two different decimal positions.

Move from left to right. A symbol after an equal or larger one is added, as in VIII = 8. In the modern spelling used here, subtraction is limited to six pairs: IV, IX, XL, XC, CD and CM. MCMXCIX can therefore be read in four groups, 1,000 + 900 + 90 + 9, to reach 1,999.

Repetition catches many wrong spellings

I, X, C and M may appear three times in a row; V, L and D do not repeat. The reverse field checks the canonical spelling after calculating the value. It rejects IIII, VV and IL rather than trying to guess what the writer intended. Clock faces may still use IIII. Visual balance is one proposed explanation, not a settled account of its origin. This historical form differs from IV in the convention used here.

Roman numbers do not include every kind of value

There is no classical symbol for zero. Negative numbers, fractions and decimal values also fall outside this conversion. The ordinary-number field accepts a whole number, including correctly placed comma grouping, and refuses trailing letters, signs or malformed separators.

Choose the direction before checking the range

The Roman numerals converter supports 1 through 3,999,999 for a number to Roman numeral conversion. From 4,000 upward it uses vinculum notation, where an overline multiplies the marked symbol by 1,000. An overlined V represents 5,000.

The reverse direction has a narrower range. Roman → Number reads the seven standard characters from 1 through 3,999 and does not accept overlined input. Use ordinary Latin letters such as IV, not the single Unicode character Ⅳ. Neither dedicated numeral characters nor overlined output can be pasted into the reverse field. Some fonts position the combining overline differently, so inspect a copied value before engraving or printing it.

Writing dates in Roman numerals

Enter day, month and year separately; the output always follows day.month.year, regardless of your regional date format. Leading zeros such as 04 are accepted. Entering a year alone converts only that year. The calendar check applies Gregorian month lengths and leap-year rules even to dates before its adoption. It does not convert ancient Roman or Julian calendar dates. Years BCE and year zero are outside its range.

The breakdown beneath a successful result shows the value contributed by each group. That is useful for checking a chapter number, cornerstone, copyright date or tattoo without repeating the same conversion by hand.