Third and mixed conditionals let you imagine a different past. Use them for regrets, lucky escapes and "what if" moments, and to connect an imaginary past with the present.
The pattern
If I had left earlier, I would have caught my flight.
If I had taken that job, I would be in Denver now.
If I spoke Spanish, I would have understood the tour guide.
01Third conditional: a different past
Use if + had + past participle, then would have + past participle. Both halves are about the past, and both are the opposite of what really happened. Swap in could have for ability and might have for a possibility.
- If we had checked the weather, we wouldn't have planned a picnic.
- She could have gotten the job if she had applied on time.
- If you hadn't called me, I might have overslept.
02Mixed conditionals: past and present together
Sometimes a past event changes your life now. Use if + had + past participle, then would + base verb.
Other times a fact that is always true about you changed a past event. Use if + past simple, then would have + past participle.
- If I hadn't moved to Seattle, I wouldn't know my husband.
- If he had saved more, he wouldn't be so stressed about rent.
- If I weren't so shy, I would have introduced myself.
- If she didn't love dogs, she wouldn't have adopted three of them.
03Quick reference
You can put either clause first. Use a comma only when the if clause comes first.
| Type | If clause | Result clause |
|---|---|---|
| Third | had + past participle | would / could / might have + past participle |
| Past cause, present result | had + past participle | would / could / might + base verb |
| Present fact, past result | past simple (were) | would / could / might have + past participle |
04What you'll hear vs. what you should write
In casual American speech, you'll often hear If I would have known, I would have called. It's very common in conversation, but it's considered incorrect in writing, at work and on tests. Use had in the if clause.
Remember that I'd can mean I had or I would: If I'd known (had), I'd have called (would).
05Common mistakes
If I would have known, I would have called.
If I had known, I would have called.
In standard English, the if clause takes had, not would have.
If she had studied, she would pass the exam last week.
If she had studied, she would have passed the exam last week.
A finished past result needs would have + past participle.
If I didn't miss the bus, I wouldn't be late now.
If I hadn't missed the bus, I wouldn't be late now.
Missing the bus was a single past event, so it needs the past perfect.
I would have went to the party.
I would have gone to the party.
After would have, use the past participle, not the past simple.