Let’s suppose you are talking about 2 events in the future:
- My computer will make 1 million calculations per minute.
- You will return from your coffee break in 20 minutes.
We can put these together and say:
By the time you return from your coffee break, my computer will have made 20 million calculations.
The Future Perfect Simple verb form then is often used to talk about an action in the future which takes place before another action.
James will have arrived in New York by the time we get up tomorrow morning.
The average American will have had 10 jobs between the ages of 18 and 38.
Forming the Future Perfect Simple
We form the future perfect by combining the future simple of the verb to have with the past particle of the main verb.
will have + past participle
will have + typed
will have + traveled
will have + eaten
Future Tense in English Grammar – talking about the future in English