Roman Numerals and How They Work

Certain parts of Roman society seem outdated by modern standards (e.g. gladiatorial battles and eating dormice). However, other parts of their culture live on, including Roman numerals.

You’ll almost certainly have seen Roman numerals used before. But do you know how they work? Or when you should use them in writing? Check out our guide below to find out.

How Do Roman Numerals Work?

Roman numerals use letters rather than the Hindu–Arabic numerals we typically use for numbers. The system works by combining letters that have specific values. These are as follows:

For most numbers, we can create a Roman numeral by adding the values above. For example:

• 6 = 5 + 1 = VI
• 27 = 10 + 10 + 5 + 1 + 1 = XXVII
• 653 = 500 + 100 + 50 + 1 + 1 +1 = DCLIII

However, if a number requires using four of the same numeral in a row, we instead subtract from the next biggest value. As such, the number four is written as ‘IV’ (i.e. 5 – 1 = 4). Examples include:

• I before V or X subtracts 1 (e.g. IX = 9)
• X before L or C subtracts 10 (e.g. XC = 90)
• C before D or M subtracts 100 (e.g. CD = 400)

So, if we wanted to write the number 999 as a Roman numeral, we would write ‘CMXCIX’.

For numbers over 3,999 the system changes a little, with lines added to existing numerals to indicate larger values up to one million.

If you can’t work out what a Roman numeral adds up to, you can use an online converter. In addition, while we’ve capitalised all of the numerals above, you can use lowercase letters instead (e.g. xix = 19).

What Are Roman Numerals Used For?

We don’t use Roman numerals for counting any more, but that doesn’t mean they’ve disappeared! These days, you still find them used for:

• Numbering the pages of introductory material in a book
• Chapter/section numbers in books and plays
• Numbering items in a list
• The year of production for films and TV shows
• Film or game sequels
• Some sporting events
• The titles of monarchs

So, while you can get by without fully understanding Roman numerals, it is useful to know the basics (especially if you ever find yourself at a showing of Rocky IV with Queen Elizabeth II). And if you want to be sure you’ve used Roman numerals correctly in writing, send us your document today.