Making a comparison with Who/Whom I now have a question about the use of what with prepositions in questions. I'll explain by example:

These two sentences are correct, one is more formal than the other:


  • Formal: With whom are you doing that?
  • Informal: Who are you doing that with?

But if I substitute Who/Whom with What, the "formal" one sounds a bit awkward and I'm not sure if it's correct or not:


  • With what are you doing that?
  • What are you doing that with?

So, are those last two questions grammatically correct?
Is one more formal than the other?

2 Answers 2


Yes, they are both grammatical, but With what are you doing that? is much more formal, and probably quite rare.


"Who are you doing that with?" is not correct. "With" is a preposition, and prepositions take objects. "Who" is subjective, and "whom" is objective. Therefore, one must use "whom" in a prepositional phrase.

"With what are you doing that?" and "What are you doing that with?" are both correct. Ending a sentence with a preposition is not incorrect, but including a preposition without its object is.

"With what..." is the more formal of the two.

  • 2
    'Who are you doing that with?' is doubtless far more common than 'Whom are you doing that with?' and probably more common than 'With whom are you doing that?' These Google Ngrams reflect this. Aug 30, 2015 at 13:58
  • 1
    So it's not a case of 'must'. It has been mentioned in other ELU threads that 'whom' is slowly disappearing from the English lexicon. Aug 30, 2015 at 14:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.