Third Conditional
B2 · Upper IntermediateConditionalsIf I had known, I would have called. A past that didn't happen — past perfect + would have, not simple past.
What you'll learn
- The third conditional uses past perfect (had + past participle) in the if-clause
- The main clause uses 'would have' + past participle
- It talks about an imaginary change to something that already happened — often a regret
- Simple past in the if-clause is not enough — the extra 'had' layer (past perfect) is essential
Imagining a different past
The third conditional looks back at something that already happened and imagines how it could have gone differently. It's often used to express regret or to point out what would have happened under different circumstances.
Past perfect, not simple past
The if-clause needs the extra 'had' layer — past perfect — not just simple past. This shows the condition happened (or didn't happen) even further back than the main clause's imagined result.
'Would have' + past participle
The main clause uses 'would have' plus a past participle to describe the imagined result. A modal like 'could have' or 'might have' can replace 'would have' depending on the meaning.
Real English
Watch out
The if-clause needs past perfect ('had known'), not simple past — simple past alone isn't enough for the third conditional.
'Would have' belongs only in the main clause — the if-clause uses past perfect ('had known'), never 'would have.'
The main clause needs 'would have' + past participle, not just 'would' + base verb, since the result is also imagined in the past.
Real life — Talking about a missed chance
"Did you hear the concert sold out?"
"Ugh, if I had bought tickets last week, I would have gone!"
"Same here. If we had checked earlier, we could have gotten seats together."
"Lesson learned — next time we won't wait."
Practice
Exercise 1 · Choose the correct sentence
Choose the correct third conditional sentence.
Exercise 2 · Choose the correct sentence
Choose the correct sentence.
Exercise 3 · Choose the correct structure
Which structure goes in the if-clause of a third conditional?
Exercise 4 · Choose the correct sentence
Choose the correct sentence about a past regret.
Exercise 5 · Choose the correct sentence
Choose the correct sentence.
Exercise 6 · Choose the correct structure
Choose the correct main clause structure for a third conditional.
Exercise 7 · Choose the correct sentence
Choose the correct sentence with a modal in the main clause.
Exercise 8 · Choose the correct sentence
Choose the correct sentence.
Exercise 9 · Complete the sentence
Complete the third conditional: 'If I ___ (know) about the meeting, I would have attended.'
Exercise 10 · Complete the sentence
Complete the third conditional: 'We would have arrived on time if the train ___ (not / be) delayed.'
Exercise 11 · Sort into groups
0 / 4 sorted
Quick challenge
Five quick questions to check what stuck.
Question 1 / 5
Score: 0/0
Choose the correct sentence.
You learned
- The third conditional uses past perfect in the if-clause.
- The main clause uses 'would have' + past participle.
- It imagines a different past — often a regret.
- Simple past alone isn't enough in the if-clause; past perfect is essential.
Related grammar lessons
Other Conditional Expressions
Learn alternative ways to express a condition — provided that, providing, on condition that, and as long as — and which register each one fits.
Second Conditional
Learn the second conditional — past simple in the if-clause, would in the main clause — for unreal or unlikely situations in the present or future.
Mixed Conditionals
Learn how to combine two different time frames in one conditional sentence — a past condition with a present result, or a present condition with a past result.
First Conditional
Learn the first conditional — present simple in the if-clause, will in the main clause — for real, likely possibilities in the future.