Study materials
These sentences look at an event from a moment when it is already over.
By Friday we will have finished the project.
By Friday the project will already be done.
By June she will have been working here for ten years.
In June it will be ten years since she started here.
The Future Perfect says an action will be over by a certain future moment. The Future Perfect Continuous counts how long it will have lasted by then. The article explains both forms, the words by, by the time and until, the tense after when and by the time, and how to choose one of the four future forms.
The Future Perfect and the word by
The Future Perfect is will have with the third form of the verb. It looks back from a moment in the future and says the action will already be behind by then. The third form of regular verbs ends in -ed, like finished, and irregular verbs have their own, like written or left.
By Sunday, we'll have painted the whole flat.
I won't have finished the report by Monday.
Will you have finished by six?
By means no later than and names that moment: by Sunday, by then, by six. By the time means at the moment when and stands before a whole clause. The sentence We'll finish it by Sunday is also correct. The Future Perfect only stresses that by Sunday the work will be done.
Until means up to, and the action goes on right up to that moment: The museum is open until six. Until is not usually used with the Future Perfect, because until counts how long an action goes on, not when it will be behind.
Will have been doing
The Future Perfect Continuous is will have been with an -ing verb. It counts how long an action will have gone on by a moment in the future, so it nearly always comes with for and a stretch of time.
By next June, she'll have been working here for ten years.
This form sounds formal and is not used without a reason. If a number of things done is named instead of time, the simple form is needed: By May, she'll have written three books. State verbs also take the simple form: Next month, we'll have known each other for twenty years.
By, by the time and until
By means no later than and often names the reference point for a perfect form: by Friday, by then, by 2030. By the time means at the moment when and stands before a whole clause. Until means up to, and the action goes on right up to that moment.
I'll have finished the essay by six.
At six it will already be done.
I'll be working on the essay until six.
The work goes on up to six.
Until usually does not take a perfect form, because until counts how long the action goes on, not when it will be behind. The sentence We'll have finished until Friday is a mistake.
No will after when and by the time
In a clause with when, before, after, as soon as, until or by the time, the future is expressed with a present tense. Will goes only in the main clause.
When the film ends, we'll go for a pizza.
To stress that one action will be over before the other, such a clause takes the Present Perfect, have with the third form.
I'll call you as soon as I've checked the tickets.
Four forms side by side
They are easy to tell apart by where you stand in your mind in relation to the action.
| Form | Where you stand | Example |
|---|---|---|
| will do | outside the event, just naming it | I'll call you tomorrow. |
| will be doing | inside the process, it is going on around you | At ten I'll be driving. |
| will have done | after the event, it is behind you | By ten I'll have arrived. |
| will have been doing | after the start, counting how long it has gone on | By ten I'll have been driving for five hours. |
Common mistakes
The first mistake is putting will in the part with when or by the time.
By the time you will arrive, we'll have finished. → By the time you arrive, we'll have finished.
The main clause already shows the future.
The second mistake is until instead of by.
I'll have finished the essay until Monday. → I'll have finished the essay by Monday.
By names the moment when the work will be over.
The third mistake is the base form after will have.
By Friday we'll have finish the project. → By Friday we'll have finished the project.
Have is followed by the third form.
The first mistake shows right after when, before or by the time. A present tense without will stands there. The second shows before the date. If the sentence has will have and the third form, by stands before the date. The third shows after have. It is always the third form, such as finished, written or gone.