si j'avais su, j'aurais

if I had known, I would have

→ si
phrase Rare #43,120
if I had known, I would have This phrase usually introduces a past action that did not happen; it is followed by a past participle.
FR: Si j'avais su, j'aurais pris un parapluie.
EN: If I had known, I would have taken an umbrella.

Si j'avais su, j'aurais agi autrement.

If I had known, I would have acted differently.

Si j'avais su, j'aurais piqué plus de bouteilles.

If I had known, I would have stolen more bottles.

— Viens chez moi, j'habite chez une copine (1981)

Si j'avais su, j'aurais mangé ailleurs.

If I’d known, I would have eaten somewhere else.

— Get Out Your Handkerchiefs (1978)

Si j'avais su, j'aurais choisi un homme bon, rassurant, mieux que le mien !

If I had known, I would have chosen a good, reassuring man—someone better than my own!

— Huit et demi (1963)

Si j'avais su, j'aurais mis une cravate.

If I’d known, I would have worn a tie.

— Independence Day (1996)

Si j'avais su, j'aurais pu offrir du café.

If I had known, I could have offered coffee.

— Dans ses yeux (2009)