B2 Upper-intermediate Conditionals, wish and modal perfect
Third conditional
Lesson goal. After this lesson you can talk about what did not happen in the past and its imagined consequence.
When to use it
- Regret about the past: If I had studied harder, I would have passed.
- Mild reproach: If you had told me, I would have helped.
- Analysing past causes and effects.
Form
| Clause | Form | Example |
|---|---|---|
| The if clause | had + V3 | If I had known, |
| Main clause | would have + V3 | I would have told you. |
| Thay would | could have / might have | I could have helped. |
| Negative | hadn't + V3 · wouldn't have + V3 | If I hadn't missed it… |
Step by step
- Identify what actually happened in the past.
- Reverse it: a positive fact becomes a negative hypothesis, and vice versa.
- The if-clause takes had + V3; the main clause would have + V3.
- Check: both halves must show a perfect form.
The three conditionals
| Type | Form | Refers to |
|---|---|---|
| Type 1 | If + present simple, will + V | a real future |
| Type 2 | If + past simple, would + V | an unreal present |
| Type 3 | If + had + V3, would have + V3 | an unreal past |
Examples
If I had studied harder, I would have passed the exam.
If we had left earlier, we wouldn't have missed the bus.
If you had told me, I would have helped you.
She wouldn't have been late if the traffic hadn't been so bad.
If they had read the map, they wouldn't have got lost.
I could have helped you if I had known.
Common mistakes
If I would have known, I would have told you. → If I had known, I would have told you.
Never put would after if — this holds for all three conditionals.
If she had studied, she would passed. → If she had studied, she would have passed.
The main clause needs all three parts: would + have + V3. Dropping have is the commonest slip.
If I had studied harder, I would pass the exam. → If I had studied harder, I would have passed the exam.
Both halves refer to the past, so the main clause needs would have + V3.
Memory tip
Count the parts: the if-clause has two (had + V3), the main clause has three (would + have + V3). A missing part means an error.
Summary
- If + had + V3, + would have + V3.
- It describes what did not happen — the facts are always the opposite.
- No would after if; never drop the have.
Practise this lesson
Do exercises with an explanation for every question, take mini tests and track your progress on GrammUp.