B2–C1

Third Conditional: Rules, Examples & Exercises

Learn the third conditional for unreal past situations, regrets and alternative past results.

Part of the ELS Conditionals Learning Path. Start with the complete conditionals guide, or study the exact area you need below.

Form

Use if + past perfect, would have + past participle.

When to use it

Use it to imagine a different past: the condition did not happen, so the result did not happen either.

Examples

If I had left earlier, I would have caught the train.
She would have passed if she had revised more.
If we had known, we would have helped.

Common mistake

Do not use would have in both clauses: ❌ If I would have known... ✅ If I had known...

Continue the Conditionals learning path

Zero ConditionalLearn when and how to use the zero conditional for facts, routines and general truths.First ConditionalMaster the first conditional for real and possible future situations.Second ConditionalUse the second conditional accurately for hypothetical, unlikely and imaginary present or future situations.Mixed ConditionalsUnderstand mixed conditionals when the condition and result refer to different times.Unless, Provided That, As Long As & Other Alternatives to IfGo beyond if: learn unless, provided that, as long as, even if, in case and other conditional linkers.If vs WhenLearn when English uses if and when in conditional and future clauses.If I Were YouUnderstand why English often says “If I were you” and when “was” is possible.Conditional SentencesFix the conditional errors English learners make most often.Conditionals ExercisesPractise all English conditional forms with targeted questions, corrections and answers.Conditionals TestTest zero, first, second, third and mixed conditionals and identify what to study next.

Test before you move on

Use the diagnostic test to find out whether your problem is form, meaning, time reference or conditional linkers.

Take the Conditionals diagnostic →

Free grammar workbook

Take this grammar point with you

Keep this lesson free online, then use the Complete English Grammar Companion for revision and extra practice. Enter your email once to unlock the free PDF.

Get the free Grammar Companion →

The lesson stays completely free. Only the optional PDF download is email-gated.