B1 · Intermediate

The third conditional: unreal past situations

Use the third conditional for a past that did not happen. You imagine a different past and its different result. It can show regret or relief.

The pattern

Third conditional
Ifhadpast participle,would havepast participle
If clauseMain clause
If I had left earlier,I would have caught the train.
If she hadn't missed the bus,she would have arrived on time.
If she had set an alarm,she wouldn't have overslept.

A past participle is the third form of the verb: understood, missed, left. See The present perfect: form and uses.

Both parts talk about the past, and both are imaginary. The real facts are the opposite: I did not leave earlier, so I did not catch the train.

Uses

Regret

  • If I had studied harder, I would have got a better grade. I did not study harder.

Relief

  • If we had taken the later train, we would have missed the wedding. We took the early train.

Criticism or blame

  • If you had told me, I would have helped. You did not tell me.

Could have and might have

In the main clause, could have (it was possible) and might have (perhaps) are also used.

  • If I had had a map, I could have found the hotel.
  • If she had asked, he might have said yes.

Questions and negatives

  • What would you have done if you had missed the flight?
  • If he hadn't helped me, I wouldn't have finished.

Clause order and the comma

You can start with either clause. Use a comma after an if clause at the start.

  • I would have called you if I had known.

Compare the three types

TypeTimeExample
Firstpossible futureIf it rains, we'll stay in.
Secondunreal nowIf it rained, we would stay in.
Thirdunreal pastIf it had rained, we would have stayed in.

See Zero and first conditionals: real conditions and The second conditional: unreal situations now or in the future. When the time of the two parts differs, see Mixed conditionals: when the time is different in the two parts. A formal version without if is on Inverted conditionals: should you need, had I known, were it to.

Watch out

✗If I would have known, I would have called.

✓If I had known, I would have called.

Would have in the if clause is heard in informal speech, and some speakers consider it incorrect. Use had + past participle.

✗If I had knew, I would have called.

✓If I had known, I would have called.

After had, use the past participle.

✗If I had known, I would called.

✓If I had known, I would have called.

The main clause is would have + past participle.

✗If I had known, I will have called.

✓If I had known, I would have called.

The result of an unreal past uses would have.

What comes next

See The second conditional: unreal situations now or in the future, Mixed conditionals: when the time is different in the two parts, Inverted conditionals: should you need, had I known, were it to, Wish and if only: wishes about now, the past and the future and Could and could have: possibilities and missed chances.

Practice

Eight questions. Choose one answer for each.