Cardinal Numbers 0-100

Spanish numbers are mostly predictable, but they are divided into "zones." The first zone is 0 to 15. These numbers are unique and don't follow a specific pattern. You just have to memorize them. The second zone is 16 to 29. These are usually written as a single word. The third zone is 30 to 99. These follow a very consistent "Tens + and + Units" formula. Finally, we have 100, which is its own special case. Understanding these zones makes the whole system feel less like a math test and more like a simple puzzle. Once you know the "tens" (20, 30, 40, etc.), you can build almost any number. It is like learning the chords to a song before playing the whole melody.

1. 1The Unique Basics (0-15): Start with cero (0) to diez (10). Then learn the "rebel" numbers: once (11), doce (12), trece (13), catorce (14), and quince (15). These don't look like the others, so give them extra love.
2. 2The Teens (16-19): These combine diez (ten) and the unit. We write them as one word: dieciséis (16), diecisiete (17), dieciocho (18), and diecinueve (19). Notice the z in diez changes to a c.
3. 3The Twenties (20-29): The number 20 is veinte. For 21-29, change the e to an i and add the unit: veintiuno (21), veintidós (22), etc. These are also written as one single word. It’s like they are holding hands.
4. 4The Tens (30-90): Learn the big milestones: treinta (30), cuarenta (40), cincuenta (50), sesenta (60), setenta (70), ochenta (80), and noventa (90).
5. 5The "Y" Pattern (31-99): For any number above 30 that isn't a clean ten, use three words. Use the Ten + y + Unit. For example, 31 is treinta y uno. 45 is cuarenta y cinco. 99 is noventa y nueve. It is very rhythmic!
6. 6The Century (100): Just say cien. If you have 100 of something, it's cien. If you go over 100, it changes to ciento, but we will save that for another day.

Use these numbers whenever you are dealing with quantities. In a job interview, you might say you have cinco years of experience. At a restaurant, you’ll ask for dos cervezas. When giving your age, remember that Spanish people "have" years, so you’d say Tengo veinticuatro años. You also use them for addresses, like Calle Mayor, número ochenta. If you are at a market, the vendor might tell you the price is diez euros. They are also vital for telling time, such as Son las cuatro (It is four o'clock). Basically, if there is a digit involved, you need these words. Think of them as your primary tools for navigating the physical world.

Don't use the full word uno when it comes right before a masculine noun. Instead, shorten it to un. For example, say un libro, not uno libro. If the noun is feminine, use una, like una mesa. Also, don't use these for the first day of the month in many countries. While you use dos de mayo, for the first, you often use the ordinal primero de mayo. Don't use y to connect hundreds to tens. In English, we say "one hundred and five." In Spanish, it's just ciento cinco. No y allowed there! Finally, don't use these for "first, second, third" in a race; those are different words entirely.

Mixing up sesenta (60) and setenta (70) is the most common blunder. Think of the s in seis for 60 and the t in siete for 70. Another mistake is putting y in the twenties. People often try to write veinte y dos, but it must be veintidós. Remember: one word for 16-29, three words for 31-99. Also, watch your accents! Numbers like dieciséis, veintidós, veintitrés, and veintiséis need them to keep the stress in the right place. If you forget them, you're not a bad person, but your teacher might shed a tiny tear. Lastly, don't forget that cero exists. It’s not "oh" like in English phone numbers; it’s always cero.

In English, we use a hyphen for numbers like "twenty-two." In Spanish, we use the word y (and) for numbers 31-99, but only for those! English speakers often want to say treinta-dos, but you must say treinta y dos. Also, English uses "teen" for 13-19. Spanish only uses a similar "prefix" pattern for 16-19 (dieci-). The numbers 11-15 are totally unique, unlike "eleven" and "twelve" which are the only unique ones in English before the "teens" start. Another contrast is gender. In English, "one" is just "one." In Spanish, uno changes to un or una depending on what you are counting. It’s a bit more sensitive to its surroundings!