Let’s talk a little bit about ending sentences with a preposition, shall we?  I know that your entire life you’ve been told that it’s not allowed.  The good news on that front is that it’s just a myth.  Most grammarians actually agree with this practice when it is needed.

Let’s begin with what is a preposition.  While generally small words, these grammatical powerhouses have a big impact on the nouns they govern.  Long story short, these little guys help us with the relationship one noun has to another.

For example:  The computer is on the desk.  

On is the preposition in this sentence telling us the where one noun (computer) is in relation to the second (desk).

If it makes sense to put the preposition at the end of the sentence, go ahead and do it.

For example:  What did you step on?  

While technically, you can say “on what did you step,” people don’t talk that way.

However, if it isn’t necessary to put the preposition at the end of the sentence, then you shouldn’t.

For example:  Where are you at?

Here, you can simply ask “where are you?” without losing any meaning.