Form

The future perfect tense is formed with will have + the past participle (the third part of the verb)

I will/shall

You will

He will

She will

It will have walked, told, seen, bought.... etc.

We will

You will

They will

The uses of the future perfect tense

This tense refers to future-before-future time. Sometimes it would be more correct to say that this tense refers to past-to-future time. Here usually the duration is included.

1. It is normally used with a time expression signalling at, by, or before which time a future event will be completed.

On May 7 he will have lived there for 5 years.

At the end of this month his mother will have been a pensioner for 10 years.

When John gets home, Mary will have passed her exam.

2. If the future end point is a time by which some future event will be completed, the time expression by is used:

By the end of June he will have read all the books on the reading list.

I will have retired by the year 2020.

3. If the future end point is a time before which some future event will be completed, the time expression before is used:

Before John gets home, Mary will have already gone.