42 in Roman Numerals

How to write 42 in Roman numerals

Roman numerals are built place by place, from the largest value to the smallest. For 42 the places are 40 (tens), 2 (ones).

1. Write 40 as XL.
2. Write 2 as II.

Joined together, XL + II gives XLII.

42 digit by digit

Check XLII by reading it back

Reading XLII from left to right and adding the pieces: XL = 40, II = 2. Together that is 40 + 2 = 42, so XLII and 42 match.

Mistakes to avoid with XLII

• Do not write the 4s and 9s additively. 42 uses subtractive pairs (XL for 40), not strings like IIII or VIIII.
• Never repeat a symbol more than three times in a row. When a fourth would be needed, the subtractive form takes over.
• Only I, X and C may be placed before a larger symbol to subtract, so XLII never contains forms such as VX or LC.
• Read XLII as one number, not letter by letter: add the values left to right, except where a smaller symbol sits before a larger one.

Facts about the number 42

• 42 is an even number and composite, with prime factors 2 x 3 x 7.
• In binary 42 is 101010 and in hexadecimal it is 2A.
• Written out, 42 is "forty-two".
• The digits of 42 add up to 6, so it is divisible by 3.

Where you will see 42 in Roman numerals

Historians read 42 as XLII when studying documents referencing the forty second year of a monarch's reign. Royal courts traditionally used Roman numerals for regnal years to align with formal state documentation standards.

Numbers near 42

More roman numerals

• 41 (XLI): previous page
• 43 (XLIII): next page
• Roman numerals chart: the full list