How to say ‘I don’t know’ in Spanish: 10 must-have phrases

How to say ‘I don’t know’ in Spanish: 10 must-have phrases

by Alison Maciejewski Cortez

Updated October 26, 2023

Wondering how to say “I don’t know” in Spanish? Don’t worry, we’ve got you covered. It’s a good sign that you’re looking up the Spanish for “I don’t know.” It means that you’re comfortable admitting when you’re lost or confused. That’s the first hurdle.

“I don’t know” happens to be an extremely useful phrase in Spanish. It tells the people around you that you need a little help. Maybe they’ll speak more slowly, define a new vocabulary term or use body language to communicate their message. With that in mind, here are ten must-have phrases for admitting that you’re lost or confused in Spanish.

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Basics of ‘I don’t know’ in Spanish

Let’s first start with the basic verb you will use for most of these phrases: saber.

How to conjugate the verb ‘saber’

Phrases that express some variation of “I don’t know” in Spanish usually require the verb saber (to know). 

You may already know how to conjugate saber in the present tense, but here’s a quick recap:

SubjectSaber (conjugated)
yo (I)
él/ella (he/she)usted (you; formal)sabe
nosotros (us)sabemos
ellos/ellas (they)ustedes (you; plural)saben

Now that we know how to conjugate saber, let’s dive right in. From beginner to advanced, here are a few different ways to say “I don’t know” in Spanish.

1. No sé

No sé is the simplest way to say “I don’t know” in Spanish. It works as an answer to any direct question you may be asked.

  • ¿En qué dirección está el museo? (What direction is the museum?)
  • No sé. No soy de aquí. (I don’t know. I’m not from here.)

2. No lo sé

Another simple phrase in Spanish for “I don’t know” is no lo sé. It’s the same basic phrase as above, but with a direct object pronoun added, which makes it more polite. No lotranslates to “I don’t know it/that” in Spanish. 

  • ¿Cuál es tu animal favorito? (What is your favorite animal?)
  • No lo sé. (I don’t know it/that.)

To be exact, lo refers to “what you just asked me.” So, in the above example, no lo means “I don’t know what my favorite animal is.”

3. No estoy segura/o

No estoy segura/o (I am not sure) is a softer and more polite way of saying “I don’t know” in Spanish. 

The word segura demonstrates a female speaker; men should say no estoy seguro. Matching the ending of the adjective segura/seguro to the speaker (female/male) is how you follow the basic rule of gender agreement in Spanish. For a progressive gender-neutral approach according to the Federación Argentina LGBT , use “e,” as in hermane (sibling) or sobrine (sibling’s child).

  • ¿Quién hace el pastel más delicioso, tu papá o yo? (Who makes the yummiest cake, your father or me?)
  • No estoy segura. (I am not sure.)

4. No me acuerdo

If you want to say “I don’t know” in Spanish and you’re talking about something you once knew but have since forgotten, use this phrase. No me acuerdo (I don’t remember) is a less direct way to express your uncertainty.

  • ¿Ale, en qué año llegaste a Holanda? (Ale, what year did you arrive in the Netherlands?) 
  • No me acuerdo. Han pasado tantos años. (I don’t remember. So many years have passed.)

5. No entiendo 

No entiendo (I don’t understand) is a useful phrase for anyone working on beginner-level Spanish. You can use this phrase to express “I don’t know what you are saying” in Spanish. 

This phrase works especially well when someone uses a big word you’ve never heard before.

  • ¿Quieres ir al museo de antropología? (Do you want to go to the museum of anthropology?) 
  • No entiendo. ¿Qué significa antropología? (I don’t understand. What does anthropology mean?)

6. Tampoco sé

If somebody already answered “I don’t know” in Spanish and you want to say that you also don’t know, use one of the two bolded phrases in the multi-person conversation below.

  • ¿Cuándo es el cumpleaños de Jorge? (When is Jorge’s birthday?)
  • No sé. (I don’t know.) 
  • No sé tampoco. (I don’t know, either.)
  • Tampoco sé y él es mi hermano. (I don’t know, either, and he is my brother.)

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7. No sé qué decir

No sé qué decir (I don’t know what to say) is a usefully vague way to express befuddlement or speechlessness in Spanish. Maybe you’ve been asked a question and you don’t have a good answer. Maybe you are overwhelmed and at a loss for words. Or maybe your level of Spanish isn’t advanced enough to respond politely and you need a delicate answer. In these cases, try this phrase.

  • Te compré flores y quiero pedirte que seas mi novia. (I bought you flowers and I want to ask you to be my girlfriend.)
  • ¿Qué puedo decir? (What can I say?)

In the above example, the awkward silence speaks for itself.

For another option in this scenario, take a cue from Twiggy and answer a trick question with another question.

  • ¿Quién es tu filósofo favorito? (Who is your favorite philosopher?)
  • No sé qué decir. ¿Quién es el tuyo? (I don’t know what to say. Who is yours?)

8. No tengo idea

No tengo idea or ni idea (I have no idea) are two fun and emphatic ways to say “I don’t know” in Spanish. 

  • ¿Quién es el mejor jugador de fútbol? (Who is the best male soccer player?) 
  • No tengo idea. No conozco a los jugadores masculinos. Sólo sigo fútbol femenino. (I have no idea. I don’t know any of the male players. I only follow women’s football.)
  • Ni idea. Todos son muy talentosos. (No clue. They are all so talented.)

9. Quién sabe

If you want a flippant and dismissive way to express your ignorance in Spanish, this answer is for you. Quién sabe (Who knows) is a good thing to say when you don’t actually care about the answer.

  • ¿Qué raza de caballo es esa? (What breed of horse is that?) 
  • Quién sabe. Todos los caballos me parecen iguales. (Who knows. All horses look alike to me.)

10. Déjame ver y te aviso

We can’t end our list without including a professional way to say “I don’t know” in Spanish. 

We often talk about using formal language if you speak Spanish in the workplace. This is another case in which it pays off to be a professional with your language. At work, instead of simply admitting that you don’t know something, it sounds better to take responsibility for finding an answer. 

  • ¿Está terminado el gran proyecto para poder presentarlo en la conferencia? (Is the huge project finished so I can present it at the conference?)
  • Déjame ver y te aviso. (Let me find out and I’ll let you know.)

Express yourself clearly…or not

Whether ending an uncomfortable conversation quickly or saving your professional reputation, it’s useful to know a few different ways to say “I don’t know” in Spanish. 

As a beginning Spanish speaker, it’s hard to say the right thing. You may not have the vocabulary to express yourself the way you do in your native language. Using these ten phrases, you can choose to be either extremely direct or politely evasive. 

Whatever the situation requires, you have a few options to respond. Which of the phrases do you think will be the most useful for you?

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Alison Maciejewski Cortez

Alison Maciejewski Cortez is Chilean-American, born and raised in California. She studied abroad in Spain, has lived in multiple countries, and now calls Mexico home. She believes that learning how to order a beer in a new language reveals a lot about local culture. Alison speaks English, Spanish, and Thai fluently and studies Turkish. Her consulting business takes her around the world and she is excited to share language tips as part of the Lingoda team. Follow her culinary and cultural experiences on Twitter.

Alison Maciejewski Cortez
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