“I will have already done my English homework by the time I eat dinner on Saturday.”

WHEN TO USE IT: The future perfect (also called the future perfect simple) tense is used to refer to an action that will be completed sometime in the future before another action takes place.

FORM: [will have + past participle] or [am/is/are + going to have + past participle]

Each of the highlighted verbs in the following sentences is in the future perfect tense.

The surgeon will have operated on 6 patients before she attends a luncheon meeting.

In this sentence, the act of operating ("will have operated") takes place in the future sometime before the act of attending ("attends").

The plumber and his assistant will have soldered all the new joints in pipes before they leave for the next job.

Here, the plumbers' act of soldering ("will have soldered") will precede the act of leaving ("leave").

By the time you get back from the corner store, we will have finished writing the thank you letters.

In this sentence, the act of returning from the store ("get back") takes place after the act of writing ("will have written").

If this year is like last year, I will have finished my holiday shopping long before my brother starts his.

In this example, the act of finishing ("will have finished") occurs well before the act of starting ("starts").

They will have written their first exam by the time we get out of bed.

Here, the act of getting out of bed occurs sometime after the writing of the exam.