How to use Roman numerals in Spanish

The Roman numeral system is based on 7 letters from the Latin alphabet. Roman numerals are used in many languages, including English and Spanish, and the circumstances that they are used in are often, but not always, the same.

In both English and Spanish, Roman numerals are notably used when referring to monarchs and popes, for example:

For those of you who need a refresher, let's look first at how Roman numerals are formed. For those who are already comfortable with using them, you can skip to Specific rules for Roman Numerals in Spanish.

The Roman numeral system

The Roman numeral system is based on 7 letters from the Latin alphabet. Each letter has a fixed value and you have to combine the letters to achieve values for which there is no single letter. The letters used in Roman numerals are:

How to read Roman numerals

When a letter is followed by another letter of the same or inferior value, the values are added together (addition):

and when a letter is followed by a letter that has a higher value, the value of the first one is subtracted from the second one:

Here are some extra rules to consider when using Roman numerals:

• Letters cannot be repeated more than 3 times
• Do not use double letters if a letter equal to that sum already

Let's look at each rule in turn.

Do not repeat a letter more than 3 times

Roman numerals cannot be repeated more than 3 consecutive times. For example, this is how the numbers 300 and 400 are expressed in Roman numerals:

It would be incorrect to repeat the letter C four times to represent 400: CCCC 

In order to indicate an amount without repeating the numeral more than three times, you have to combine the letters using subtraction.

For example, to represent the value 400 in Roman numerals, you use the next highest Roman numeral: D (=500) and the value that needs to be subtracted to achieve the correct amount is placed in front: C (100). Let's look at this example step-by-step:

Do not use double letters if there is a letter equal to that value

Do not repeat a letter if there is already a Roman numeral that represents that value.

For example, to say 10, we must use: X (=10), not VV (=5+5)

With all these rules in mind, let's look at some examples with different numbers:

Specific rules for Roman Numerals in Spanish

Some things to consider when using Roman numerals in Spanish are that how you write them depends on whether what they are referring to are in upper or lower case.

Referring to lower case nouns 

In Spanish, when the Roman numeral is referring to a noun that is written in lower case, it is recommended that you write the Roman numeral in small capitals. Small capitals are graphically identical to the form of the capital letter but with the size of the  lower case letters they accompany. For example:

this is the recommended way rather than:  páginas XX - XXII / páginas xx-xxii and siglo XXI / siglo xxi

Referring to upper case/capital letter nouns

In Spanish, if the Roman numeral is accompanying a noun that is written in or starting with a capital letter, it is recommended practice to write the Roman numerals in capital letters as well. For example, when referring to kings and queens or wars:

General contexts where Roman numerals are used in Spanish

Nowadays Roman numeral are used in Spanish in the following contexts.

Note that is this section we are going to refer to cardinal and ordinal numbers. Examples of cardinal numbers are uno, dos, tres / one, two, three, examples of ordinal numbers are primero, segundo, tercero / first, second, third. If you need a handy way to remember the difference, think about cardinal numbers being used for counting and ordinal numbers being used for order.

Centuries

Although in most contexts the Roman numerals are read as ordinal numbers (primero, segundo, décimo tercero...), in Spanish when referring to centuries starting from the eleventh century (siglo XI) this is generally read as a cardinal number [once, doce, trece], while centuries earlier than the 11th century, both ordinal and cardinal numbers can be used indistinctively (e.g. siglo V can be enunciated as siglo cinco OR siglo quinto).

However it is incorrect to write it using the cardinal number in digits or numbers expressed in words. You must use Roman numerals. This would be incorrect:

Monarchs and Popes

Roman numerals are used to refer to popes, emperors, and monarchs generally. In this case, the Roman numeral is generally read as an ordinal number  (primero, segundo, décimo tercero...), and placed after the name:

Events

To talk about events, i.e. congresses, fairs... the Roman numeral is placed before the noun and read as an ordinal number:

Compare this usage to the most famous event in the English-speaking world to use Roman numerals: the Super Bowl. Note how they are placed after the event name: Super Bowl LVI.

Books and plays

In Spanish, books and plays use Roman numerals to specify the scene or the chapter.

Although scenes or chapters in a book can use a cardinal number or an ordinal number using the regular arabic numbers: capítulo 3, escena 2.ª... you will also find Roman numerals, placed after the noun:

Lessons with more detail on Cómo Usar Los Números Romanos En Español (How to use Roman numerals in Spanish)

• How to express centuries in Spanish with Roman numerals