There are different structures of mixed conditionals, but we will focus on the two most common ones, which are a combination of the second and third conditional.

If + subject + past perfect, subject + would + verb in infinitive

If + subject + past simple, subject + would + have + verb in past participle

Remember the past participle will be formed by adding the particle -ed at the end of a regular verb, or by looking up the past participle form in the list of irregular verbs if the verb is not regular.

Other modal verbs such as could or might can be used instead of would:

	Mixed conditional
Would	If I had seen the film, I would tell you what it's about.
Would	If I had more money, I would have bought you a present.
Could	If I had finished earlier, I could be there with you now.
Could	If you knew the truth, you could have told me.
Might	If you had gone to the doctor, you might feel better now.
Might	If I weren't so shy, I might have asked her out.

Like all conditionals, the order of the two sentences can be changed. If we start with the condition (if) we will separate them by a comma. If we start with the sentence that expresses the result we don't put a comma.

3. How are mixed conditionals used?

We have two different structures, so their use will depend on what we want to express.

When we want to express that an action that took place in the past has a result in the present. In this case the part of the condition (if) will be in past perfect (third conditional) and the part that expresses the result will be with would + verb in infinitive (second conditional).

If + subject + past perfect, subject + would + verb in infinitive

If I had taken the underground, I wouldn't be in a traffic jam.

If you hadn't gone to bed so late, you wouldn't feel sleepy now.
When we want to express a probable result in the past about a situation that is not real in the present. In this case the part of the condition (if) will be in past simple (second conditional), and the sentence that expresses the result will be with would have + verb in past participle (third conditional).

If + subject + past simple, subject + would + have + verb in past participle

If I had more willpower, I would have given up smoking long ago.

In this example, we express a probable result in the past (give up smoking) about a situation (have a will) that is not real or does not happen in the present.

If I were fitter, I would have finished the race.

In this example, the likely result in the past (finish the race) would have occurred if the situation in the present (be fit) was different from reality (he is not fit at the moment).

Remember!

Structure
IF + PAST PERFECT + WOULD + VERB INFINITIVE	IF + PAST SIMPLE + WOULD + HAVE + VERB PAST PARTICIPLE

Use
When we want to express that an action that took place in the past has a result in the present	When we want to express a probable result in the past about a situation that is not real in the present

Examples
If you had eaten your lunch, you wouldn't be hungry now.	If your answer were incorrect, I would have told you.