I’m normally very cautious about not correcting people’s grammar in daily speech, for fear of coming off as an inveterate snob. As a matter of fact, it makes me very self-conscious when people not preparing for the SAT or the ACT make jibes about how they’d better watch their grammar around me. Unless explicitly asked to comment, I keep my mouth shut. That said, the one thing that truly makes me grimace when I hear it in public conversation is a statement along the lines of the following:

“Well, if we only would have known the store was going to close at 6, we would have come sooner.”

I confess, I practically have to physically restrain myself from commenting; it’s like nails screeching on a blackboard. I know that the construction is (unfortunately) common, but it’s still flat-out wrong.

Here’s the short version of the rule: a clause beginning with if should contain have, not would have. However, a different clause in the same sentence may contain would have

The reason is that both would and if both signal the conditional — that is, they refer to events that could have happened but that did not actually happen. To include both of these terms in the same clause is therefore redundant.

Incorrect: If we would have known the store was going to closer, we would have come sooner.

The sentence can also be correctly written this way:

Correct: If we had known the store was going to closer, we would have come sooner.

Correct: Had we known the store was going to closer, we would have come sooner.

So If I would have, If you would have, If they would have…. All wrong. The correct phrases are, If I had, If you had, If she had, etc.

So the next time you start to say, “If I would have only known…” you might want to think twice.