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Which one to use?Advancedstructurestructure
Will have donevsWill have been doing
'Will have done' emphasizes completion before a future point; 'will have been doing' emphasizes the duration of the ongoing action.
Side-by-side comparison
Will have done
structureThe future perfect ("will have done") talks about an action that will be complete at a specific point in the future. It emphasizes the finished result.
By Friday she will have finished writing all the thank-you cards.
By this time tomorrow the painters will have finished the living room.
They will have eaten by the time we arrive, so let us eat before we go.
Will have been doing
structureThe future perfect continuous ("will have been doing") talks about an action that will have been in progress up to a point in the future. It emphasizes how long the process has been going on.
By next month I will have been learning English for exactly one year.
By the time she retires, she will have been teaching at the same school for thirty years.
We will have been waiting for two hours by the time the train finally arrives.
Common mistake
- •"I will have working for three years" is wrong: "been" is mandatory in the future perfect continuous ("I will have BEEN working").
- •And with completion verbs like "finish", the continuous sounds unusual: "I will have been finishing" is not natural.
- •Use simple for results ("will have finished") and continuous for ongoing processes ("will have been working").
Trick to remember it
- •Emphasis on something being COMPLETED? "Will have done".
- •Emphasis on the DURATION of the process? "Will have been doing".
- •With "for + duration" (for three years): the continuous is more natural.
- •Stative verbs (know, own, be): never in continuous, always simple.
Quick rule
- •"Will have + participle" = completed before a future point.
- •"Will have been + gerund" = in progress up to a future point.
- •"BEEN" is mandatory in the continuous.
Did you know?
The future perfect and future perfect continuous are the least frequent tenses in everyday conversational English, in informal speech they are usually replaced by "will be done" or "should be done" or phrases like "I'll have it ready by Friday." However, they are very common in legal, academic, and formal business English, where temporal precision is essential. In contracts, the future perfect simple describes conditions precedent: "The buyer will have completed due diligence before the closing date", with real legal consequences if not fulfilled.
Practise what you learned
Exercise 1 · Pick the right one
By next year, she _____ living in London for a decade.
Exercise 2 · Pick the right one
By the time the meeting starts, they _____ waiting for two hours.
Exercise 3 · Form the word
Related word pairs
By the timevsBy
'By the time' introduces a full temporal clause; 'by' is a preposition followed by a noun or time expression.
Present perfect simplevsPresent perfect continuous
Present perfect simple indicates a result or completed action; continuous emphasizes duration or an ongoing activity.
So farvsUntil now
'So far' and 'up to now' describe what has happened until now neutrally; 'until now' implies something is about to change.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy