Spanish Numbers 0–999: Uno, Veintiuno and the Hundreds

Spanish numbers are built from a small set of words and a few rules. Up to 29, each number is one word. For 31–99, the usual spelling joins tens and a non-zero unit with y: treinta y uno; round tens stay one word, such as cuarenta. Add two details — uno and the hundreds agree with the noun, and 100 is cien but 101 is ciento uno — and you can build numbers up to 999.

0 to 29: one word each

The numbers up to 15 simply have to be learned. From 16, a pattern starts: dieci- + the unit for 16–19, and veinti- + the unit for 21–29, always written as one word.

Pronunciation note: in most of Spain, c before e or i and z sound like th in English think: cero, cinco, doce, diez. In Latin America, the Canary Islands and parts of Andalusia they sound like s. Both are standard. The second c in cinco, before o, has a k sound everywhere.

30 to 99: tens + y + units

Learn the tens, then add a unit with y (“and”). When both are present, the usual spelling has three words: treinta y uno, cuarenta y dos. This guide uses those spellings.

The y appears only between tens and units. It's not used in 16–29, which are already one word, and not after the hundreds: ciento veinte, trescientos cuarenta y uno.

Uno, un or una?

Use uno to name the number or count. Before a noun, use un with a masculine noun and usually una with a feminine one. Numbers ending in uno follow the same pattern. If the noun is omitted, its gender can still matter: ¿Cuántas hermanas tienes? —Una. (“How many sisters do you have? — One.”)

Notice the accent on veintiún. Standard agreement requires veintiuna personas and treinta y una personas, not veintiún personas. A special case is a feminine noun beginning with stressed a: un águila, veintiún águilas. The noun remains feminine.

100 to 999: cien, ciento and the hundreds

Cien or ciento? Say cien for exactly 100, on its own or before a noun. From 101 to 199, use ciento + the rest of the number, with no y after it.

The hundreds. Most are the unit + -cientos, but three are spelled differently. From 200, the hundreds also have a feminine form in -as.

Cien and ciento never change for gender: cien personas, ciento veinte personas. The next step is mil (1,000), which is just mil, not un mil.

Writing digits: decimals can use a comma or a point — 2,5 and 2.5 are both valid, and local habits vary. For grouping thousands, the standard recommendation is a space for numbers with more than four digits: 15 000. Four-digit quantities are normally ungrouped: 1500. You will still see 1.500 and 1,500 in everyday use; check the context.

Common mistakes

Uno before a noun, or un before casa. Use un hermano and una casa, matching the noun’s gender.

Cien y cinco for 105. Cien is only for exactly 100; after it comes ciento, and there is no y between the hundreds and the rest.

Masculine hundreds with a feminine noun. From 200 to 900, the hundreds agree with the noun.

A missing y or a missing accent. In the usual separate-word spellings for 31–99, put y between tens and units. The numbers 16, 22, 23 and 26 need a written accent.

In older texts you may see diez y seis or veinte y dos. Those spellings are out of use today; the standard is one word: dieciséis, veintidós.

Quick exercise

Write the number in words. For 31–99, use the usual separate-word spelling taught above. Make the number agree with the noun where needed.

1. Mi hermana tiene ___ años. (22)
2. Solo tengo ___ hermana. (1)
3. Hay ___ libros en la mesa. (21)
4. Enero tiene ___ días. (31)
5. Mi abuelo tiene ___ años. (96)
6. El abrigo cuesta ___ euros. (100)
7. La bici cuesta ___ euros. (150)
8. En el concierto hay ___ personas. (500)