We use the future perfect tense to say that something will already be done, finished, or completed by some time in the future.

This verb tense is not used a lot, but it is worth knowing if you want to be a fluent or advanced English speaker.

We can make the future perfect tense in two ways. We can use "will" or "be going to".

Subject + will have + past participle…

• I will have finished all of my homework by 6 pm tonight.
• She will have seen all of his movies after she watches this one.
• They will have saved enough money to buy a house by next year.

Use "will not have" to make a negative sentence.

• I will not have finished all of my homework by 6 pm tonight.

Subject + be verb + going to have + past participle…

• I am going to have finished all of my homework by 6 pm tonight.
• She is going have seen all of his movies after she watches this one.
• They are going to have saved enough money to buy a house by next year.

Use "be verb + not + going to have" to make a negative sentence.

• They are not going to have saved enough money to buy a house by next year.

There are two main ways that we use the future perfect tense.

1. We use it to say that something will happen before another action or event in the future. Or that something will happen before a specific time in the future. These sentences usually go with "by + (time)", "before", or "when".

• I will have finished everything by next Friday.
• They will have arrived by 5 pm tomorrow.
• She is going to have used all of the materials by early next week.
• I will have finished everything before you arrive.
• She will have prepared all of the food when you arrive.

2. We can also use the future perfect tense to show that something will continue until another time in the future or until another action begins in the future.

• I will have been in Tokyo for a year by the time I leave.
• She is going to have worked here for 10 years by the end of next month.

Remember that we do not use the future perfect tense after time clauses (when, before, after, unless, etc.)

• I will go when I will have finished my work.

In these cases, we use the present perfect or we switch the order of the sentence and put the future perfect tense at the beginning of the sentence.

• I will go when I have finished my work.
• I will have finished my work when I go.
• I will have finished my work by the time I go.

We can also put the time phrase at the beginning of the sentence.

• By next Monday, we will have finished everything.
• By next year, he will have saved enough money to buy a car.

Here is how you make a yes/no question.

Will + subject + have + past participle…?

• Will you have arrived by 3 pm tomorrow?
• Will he have become a fluent English speaker by next year?

Be Verb + subject + going to have + past participle…?

• Are you going to have arrived by 3 pm tomorrow?
• Is he going to have become a fluent English speaker by next year?

Here is how we can make questions with question words.

Question Word + will + subject + have + past participle…?

• What time will he have arrived by?
• When will he have decided by?
• What work will you have completed by the deadline?
• How many countries will you have visited by the end of your trip?

Even though this not a very commonly used verb tense, it is worth knowing. You can get more familiar with the future perfect tense in the next free English grammar lessons. If you want to speak English fluently, then you must know this advanced English grammar point. Even though you might not use it a lot when you speak English, you at least need to know it for reading and listening.