If I had known…
Third conditional
For the past that didn't happen: if + had done, then would have done: If I had known, I would have come.
- If I'd known, I would have come.
- If we hadn't missed the bus, we'd have been on time.
- She would have passed if she had studied.
«Si lo hubiera sabido, habría venido»: hubiera sabido is had known, habría venido is would have come.
No would in the if half: If I had known (not if I would have known). 'd can mean had or would: If I'd known = had; I'd have come = would.
Also on this page: could have, might have · I wish I had… · If I had… (the second conditional)
Try 6
Six quick questions, easiest first. At the end you'll see which mistake you make.
- If the villagers ______ the forest, the animals might not have lost their habitat.haven't destroyed · wouldn't have destroyed · hadn't destroyed · didn't destroy
- We ______ so late if we had listened to the weather forecast.wouldn't set off · didn't set off · wouldn't have set off · hadn't set off
- If I ______ the climbing club, I would never have met my best friend.hadn't joined · wouldn't have joined · didn't join
- If you'd asked me, I ______ you move house last weekend.would have helped · would help · will help
- If more people ______ aware of the problem, the river would not have become so dirty.would be · have been · had been · would have been
- We ______ the train if the taxi had arrived on time.wouldn't miss · wouldn't have missed · didn't miss
- If Maya ______ plastic bottles earlier, she would have produced much less rubbish.gave up · had given up · would give up · has given up
- Tom's school would have met its recycling target last term if more students ______ the new bins.would have used · used · would use · had used
- Lucy ______ left out last Saturday if someone had invited her to the barbecue.didn't feel · wouldn't have felt · wouldn't feel
- If the printer ______ down this morning, the report would have been ready on time.didn't break · hadn't broken · wouldn't have broken
- If Jake ______ my number, we would have stayed in touch after university.hadn't lost · wouldn't have lost · didn't lose
- My brother ______ to my wedding last month if his flight hadn't been cancelled.came · would have come · would come
Show the answers
- hadn't destroyednot didn't destroy: I did after if, for the pastnot haven't destroyed: have done after ifnot wouldn't have destroyed: would or would have after if
- wouldn't have set offnot wouldn't set off: would without have, for the past
- hadn't joinednot didn't join: I did after if, for the pastnot wouldn't have joined: would or would have after if
- would have helpednot would help: would without have, for the past
- had beennot would be: would or would have after ifnot have been: have done after ifnot would have been: would or would have after if
- wouldn't have missednot wouldn't miss: would without have, for the past
- had given upnot gave up: I did after if, for the pastnot has given up: have done after ifnot would give up: would or would have after if
- had usednot used: I did after if, for the pastnot would use: would or would have after ifnot would have used: would or would have after if
- wouldn't have feltnot wouldn't feel: would without have, for the past
- hadn't brokennot didn't break: I did after if, for the pastnot wouldn't have broken: would or would have after if
- hadn't lostnot didn't lose: I did after if, for the pastnot wouldn't have lost: would or would have after if
- would have comenot would come: would without have, for the past
Common mistakes on this point
Not: If I would have known, I would have come.
Say: If I had known, I would have come.
After if, use had + the third form (know, knew, known): If I had known…
See this mistake on its own page ›Not: If they didn't destroy the forest, the animals wouldn't have lost their home.
Say: If they hadn't destroyed the forest, the animals wouldn't have lost their home.
For a past event that didn't happen, the if half takes had done: If they hadn't destroyed…
See this mistake on its own page ›Not: If you had asked me, I would help you.
Say: If you had asked me, I would have helped you.
For something that didn't happen in the past: would have + the third form (would have helped, would have gone).
See this mistake on its own page ›Not: If more people have been careful, the river wouldn't have got dirty.
Say: If more people had been careful, the river wouldn't have got dirty.
For the past, the if half takes had done, not have done.
See this mistake on its own page ›