Explanation

Quick Answer

Just like in English, Spanish cardinal numbers (números cardinales) can be both nouns and adjectives. But before we get into that, let's learn how to say the numbers in Spanish from 0 to 100 (los números de cero a cien).

Cardinal numbers denote quantity, as opposed to order. To talk about order, you can use ordinal numbers.

Basic Cardinal Number Forms

Here are the numbers from 0 to 20, as well as the multiples of 10 from 10 to 100.

Numeral	Spanish	Numeral	Spanish
0	cero	15	quince
1	uno	16	dieciséis
2	dos	17	diecisiete
3	tres	18	dieciocho
4	cuatro	19	diecinueve
5	cinco	20	veinte
6	seis	30	treinta
7	siete	40	cuarenta
8	ocho	50	cincuenta
9	nueve	60	sesenta
10	diez	70	setenta
11	once	80	ochenta
12	doce	90	noventa
13	trece	100	cien/ ciento
14	catorce

Twenties

The numbers from 21 to 29 use a combination of veinti- and a number from 1-9 (with no space in between).

Numeral	Spanish
21	veintiuno
22	veintidós
23	veintitrés
24	veinticuatro
25	veinticinco
26	veintiséis
27	veintisiete
28	veintiocho
29	veintinueve

When veintiuno is used before a noun, such as the word años(years), it changes to veintiún.

examples
¿Cuántos años tienes? - Veintiuno. How old are you? - Twenty-one.
¿Tienes veintidós? - No, tengo veintiún años. Are you twenty-two? - No, I'm twenty-one years old.

examples

¿Cuántos años tienes? - Veintiuno.

How old are you? - Twenty-one.

¿Tienes veintidós? - No, tengo veintiún años.

Are you twenty-two? - No, I'm twenty-one years old.

Note that veintidós, veintitrés, and veintiséis and have an accent on the last syllable.

31-99

Forming the numbers from 31 to 99 is a cinch. You just use a multiple of 10 plus the conjunction y and a number from 1 to 9. Here are some examples.

Numeral	Spanish
31	treinta y uno
42	cuarenta y dos
53	cincuenta y tres
64	sesenta y cuatro
75	setenta y cinco
86	ochenta y seis
97	noventa y siete

When to Use Cardinal Numbers

Besides being used to simply count, cardinal numbers are used in Spanish to tell the time and talk about dates and age.

Telling Time

To tell the time in Spanish, you use the verb ser, a feminine definite article (la or las), and a cardinal number.

examples
Son las ocho. It is eight o'clock.
Es la una de la tarde. It's one in the afternoon.

Dates

To talk about dates, use the masculine singular definite article (el) and a cardinal number.

To talk about the first of the month, you use the ordinal number primero(first) instead of the cardinal number uno.

examples
Hoy es el diecinueve de mayo. Today is May 19th.
El primero de enero es mi cumpleaños. January 1st is my birthday.

Age

To talk about age, use the verb tenerand a cardinal number.

examples
Yo tengo veinticuatro años. I am twenty-four years old.
Mi hermana tiene treinta y nueve años. My sister is thirty-nine years old.

Cardinal Numbers as Adjectives

As mentioned before, cardinal numbers can be both nouns and adjectives. When a cardinal number is used as an adjective, it doesn't change to match the gender or number of the noun it modifies except in the cases of uno and cien.

Uno

Uno becomes unwhen used to describe masculine nouns and unawhen used to describe feminine nouns. Numbers ending in uno (veintiuno, treinta y uno, etc.) also undergo these changes.

examples
Tengo un libro. I have one book.
Mandé treinta y una cartas. I sent thirty-one letters.

Cien

Cien changes to ciento in numbers above 100 and changes according to the gender of the noun.

examples
Jorge contó hasta cien. Jorge counted to a hundred.
Llegaron ciento y diez personas. One hundred ten people showed up.
Quiero trescientos libros. I want three hundred books.
Hay doscientas casas en este barrio. There are two hundred houses in this neighborhood.