After you know the Spanish numbers, you can sound like a native Spanish speaker by paying attention to the nuances of pronouncing and writing the numbers. Here are the rules to remember when using cardinal numbers in Spanish:

  • Uno (one), used only when counting, becomes un before a masculine noun and una before a feminine noun, whether the noun is singular or plural:

    • uno, dos, tres (one, two, three)

    • un niño y una niña (a boy and a girl)

    • sesenta y un dólares (61 dollars)

    • veintiuna (veinte y una) personas (21 people)

  • You use the conjunction y (and) only for numbers between 16 and 99. You don’t use it directly after hundreds:

    • ochenta y ocho (88)

    • doscientos treinta y siete (237)

  • You generally write the numbers 16–19 and 21–29 as one word. The numbers 16, 22, 23, and 26 have accents on the last syllable:

    • 16: dieciséis

    • 22: veintidós

    • 23: veintitrés

    • 26: veintiséis

  • When used before a masculine noun, veintiún (21) has an accent on the last syllable:

    • veintiún días (21 days)

    • veintiuna semanas (21 weeks)

  • Ciento (100) becomes cien before nouns of either gender and before the numbers mil and millones. Before all other numbers, you use ciento. Un (one), which you don’t use before cien(to) or mil, comes before millón. When a noun follows millón, you put the preposition de between millón and the noun. Millón drops its accent in the plural (millones):

    • cien sombreros (100 hats)

    • cien blusas (100 blouses)

    • cien mil millas (100,000 miles)

    • cien millones de dólares (100 million dollars)

    • ciento noventa acres (190 acres)

    • mil posibilidades (1,000 possibilities)

    • un millón de razones (1,000,000 reasons)

  • In compounds of ciento (doscientos, trescientos), there must be agreement with a feminine noun:

    • cuatrocientos pesos (400 pesos)

    • seisientas pesetas (600 pesetas)

  • You use cardinal numbers when expressing the first part of an address:

    • mil seiscientos Avenida Pennsylvania (1600 Pennsylvania Avenue)

English speakers generally write the number 1 in one short, downward stroke. In the Spanish-speaking world, however, the number 1 has a little hook on top, which makes it look like a 7. So to distinguish a 1 from a 7, you put a line through the 7.

When it comes to numerals and decimals, Spanish uses commas where English uses periods, and vice versa:

Commas and Periods in English and Spanish Numbers
English Spanish
6,000 6.000
0.75 0,75
$1,999.99 $1.999,99