Grammar - Future Perfect Tense

The FUTURE PERFECT TENSE indicates that an action will have been completed (finished or "perfected") at some point in the future. This tense is formed with "will" plus "have" plus the past participle of the verb (which can be either regular or irregular in form): "I will have spent all my money by this time next year. I will have run successfully in three marathons if I can finish this one."

Singular    Plural
I will have walked    we will have walked
you will have walked    you will have walked
he/she/it will have walked    they will have walked

Singular    Plural
I will have slept    we will have slept
you will have slept    you will have slept
he/she/it will have slept    they will have slept

Singular    Plural
I will have been    we will have been
you will have been    you will have been
he/she/it will have been    they will have been

By this time next week, I will have worked on this project for twenty days.
Before he sees his publisher, Charles will have finished four chapters in his new novel.
A Democratic president will have been in the White House for nearly half of the twentieth century.
How long will it have been since we were together?

http://grammar.ccc.commnet.edu/grammar/tenses/future_perfect.htm#perfect