Bonjour Tristan !

Use

The future perfect simple is used to describe an action that takes place before another in the future. It is a kind of “past in the future”.

Example:
Quand j’aurai pris mon bain j’irai au supermarché. (When I have taken my bath I will go to the supermarket.)

Here the first action “take a bath” is put before the second action “go to the supermarket”. “to take a bath” is therefore put in the future perfect simple “I will have taken my bath” and “to go to the supermarket” in the future simple “I will go to the supermarket”. You will notice that the two times (future simple and future perfect) are used together and that the future perfect needs the future simple. On the other hand, it is never used with the near future.

Formation

The future perfect is one of the compound tenses of French. To form it it is necessary to know the simple future and the past participles that are used to form the compound past. The formation of the future perfect is almost identical to that of the past tense, with the exception of the auxiliary “to be or to have” which is put in the simple future.

Être/avoir au futur simple + participe passé

Note: The future perfect is often used with “when”.

Some examples:

“Maman, je veux une glace!
Tu auras une glace quand tu auras fini tes haricots verts”

“Mom, I want an ice cream!

You will have an ice cream when you will have finished your green beans”

“Quand j’aurais réussi mes examens je serai professeur de français”

“When I will have passed my exams I will be a French teacher”

“Quand je serai devenu riche j’achéterai une péniche à Paris, en face de la tour eiffel.”

“When I will have become rich I will buy a barge in Paris, in front of the Eiffel Tower.”

To go further and boost your French I recommend you check my video course, or if you want a personalized approach, special project, need a teacher or talk to me in private contact me for a private lesson.

Other Resources: French Language Exercises, Columbia edu