Third Conditional Phrases

This lesson explains how to use the third conditional. It is part of a complete B2 English course. The exercises for this topic are here.

If you want to revise other conditionals check out the zero, first and second conditionals. There is a presentation version of this material in the “materials” tab above.

What is the Third Conditional?

Third conditional phrases describe imaginary / hypothetical events in the past and their imaginary consequences in the past.

Imagine that I missed your birthday. I didn’t know that it was your birthday, but I find out the next day. I feel bad because I didn’t buy you a present. I could say…

“If I had known it was your birthday I would have bought you a present.”

In reality, I didn’t know that it was your birthday, I didn’t you a present. But if, in an imaginary world, I had known that it was your birthday, then I’m sure that I would have bought you a present.

How to form the third conditional

Third conditional phrases are formed like this:

If + Past Perfect / would have + past participle.

The third conditional uses the subjunctive mood. In the subjunctive “were” is used for all persons in place of “was”.

“Would” can be substituted with other modal verbs such as “could”, “might” or “may”. Note that “would can” is not grammatical, “could” is the conditional form of “can”.

Examples of the third conditional

If I had studied more I might have passed the test.1

If I hadn’t missed the bus I would have arrived on time.

I wouldn’t have passed the test if you hadn’t helped me to revise.2

I wouldn’t have asked for help unless I had really needed it.3

Had I arrived on time I wouldn’t have missed the start of the film.4

  1. This examples shows the use of “might” used in place of “would” as an alternative modal verb.
  2. Here you can see that the two clauses (If… & would..) can be inverted with no change in meaning.
  3. This example substitutes “if” with “unless”, meaning “if not”.
  4. This sentence shows an “inversion” of the subject and auxiliary. You can find out more about inverting third conditionals here.

What is the difference between the third conditional and other conditionals?

The second and third conditionals refer to imaginary or hypothetical situations. The second conditional describes imaginary present and future situations, the third conditional describes imaginary / hypothetical situations in the past.

0 / zero conditionalif + present / presentThings that are always true.If students don’t study they don’t learn.
1st / first conditionalif + present / will + infinitive without “to”Probable situations & their consequencesIf I go to the shop I will buy some milk.
2nd / second conditionalif + past / would + infinitive without “to”Imaginary / hypothetical present & future situations & their consequences.If I saw a monster I would be afraid.
3rd / third conditionalIf + past perfect / would + have + past participleImaginary / hypothetical past situations & their consequences in the past.If I hadn’t drunk coffee before I went to bed last night I would have slept better.

Mixed Conditionals

2nd and 3rd Conditionals can be mixed.

“If I were more confident I would have got the job.”1

“If I had got better exam results when I was a teenager I would earn more now.”2

1 This example starts with the 2nd conditional for an imaginary present state and ends with an imaginary past event that is a consequence of not being more confident.

2 This sentence starts with an imaginary past event using the 3rd conditional form and


Check that you understand this topic with these interactive exercises.