I wonder if my understanding of the meanings implied in these sentences is right. Besides, I would like to know how common they are in every day English and whether they can be used interchangeably when you want to ask someone what they are going to do tonight - I'm asking so because of the approximation between "want" vs "plan" meanings.

What are you up for tonight? (this one bluntly means "What do you want to do tonight?")

Reference: http://dictionary.cambridge.org/dictionary/learner-english/be-up-for-sth)

be up for sth informal
› to want to do something: We're going clubbing tonight if you're up for it.

What are you up to tonight? (this one is about the 3rd definition below, the on related to "devising" and "scheming".

Reference: http://idioms.thefreedictionary.com/up+to

up to

  1. As far as or approaching a certain point. For example, The water was nearly up to the windowsill, or They allowed us up to two hours to finish the test, or This seed should yield up to 300 bushels per acre. [c. a.d. 950]

  2. be up to. Be able to do or deal with, as in When I got home, she asked if I was up to a walk on the beach. This usage is often put negatively, that is, not be up to something, as in He's not up to a long drive. [Late 1700s]

  3. Occupied with, engaged in, as in What have you been up to lately? This usage can mean "devising" or "scheming," as in We knew those two were up to something. It also appears in up to no good, meaning "occupied with or devising something harmful," as in I'm sure those kids are up to no good. [First half of 1800s]

  4. Dependent on, as in The success of this project is up to us. [c. 1900] Also see the following idioms beginning with up to.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

  • 2
    The idiom "up for" means "what are you willing to do?" And "up to" means "what are you planning to do?". The perhaps non-obvious distinction is in the former case (for), the understanding is you and I (asker and answerer) will be spending the evening together, and in the latter case (to), the understanding is we will not (if I have to ask you what you've already planned for the evening, then clearly I know I'm not part of your plans).
    – Dan Bron
    Jan 8, 2015 at 13:14
  • Thanks, Dan! That's a valid and interesting point you made. Can I understand by your words that both are commonly used AND with the distinction you pointed out?
    – Thiago
    Jan 8, 2015 at 13:21
  • Thiago: Yes, they're both in common use among regular people, at least where I live (New York).
    – Dan Bron
    Jan 8, 2015 at 13:23
  • What @Dan said. This is all General Reference (not that it would be easy to glean that information from the unformatted text of the definitions as currently cited by the question). I don't know exactly how be up for sth came to have the sense of be prepared/willing/keen to do sth, but it seems likely to me it's a figurative allusion to standing up/putting one's hand up to volunteer for something. The "etymology" of to be up to sth is (inconclusively) explored here. Jan 8, 2015 at 13:24
  • Thanks again, Dan! Great contribution, FumbleFingers, really appreciated it.
    – Thiago
    Jan 8, 2015 at 14:03

1 Answer 1


Colloquially, if A asks B, what are you up for tonight?, A would be inquiring what B would like to do tonight. There is an implication contained that A is interested in making or proposing an arrangement.

If A asks B, what are you up to tonight A would, ostensibly at least, be inquiring as to what B's plans were for the evening. Equally A may be about to suggest something but that much is not implied in the question, as it would be in the previous example.


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