Which of the following is correct?

  1. Which one do you want?
  2. What one do you want?

If you're offering a limited choice, then use which: "Which of these 25 models do you want (to buy/try/look at)?"


But if there are endless possibilities, use what: "Now that you've won the lottery, what do you want to buy, a Rolls, a Benz, a Ferrari, a Lamborghini?"

"What one do you want?" isn't idiomatic English, but "Which one do you want?" is.


In American English, which one is a common phrase. What one is not, and it sound very stilted.


Which is used to refer to a specific object, while what is referring to a more general selection.

In your case, "which one" do you want is correct. You can also change it to be "what do you want".

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