The Future Perfect Continuous Tense
The Future Perfect Continuous Tense isn't used very much in English and it is a little complicated to make. However, at higher levels it is great to understand it, and maybe use it sometimes too. It has a very precise meaning which can be convenient.
Positive Form Positive Short Form
I will have been working I'll have been working
You will have been sleeping You'll have been sleeping
She will have been studying She'll have been studying
He will have been cooking He'll have been cooking
It will have been raining It'll have been raining
We will have been exercising We'll have been exercising
They will have been travelling They' ll have been travelling
Negative Form Negative Short Form
I will not have been working I won't have been working
You will not have been sleeping You won't have been sleeping
She will not have been studying She won't have been studying
He will not have been cooking He won't have been cooking
It will not have been raining It won't have been raining
We will not have been exercising We won't have been exercising
They will not have been travelling They won't have been travelling
'Yes / No' Questions
Will I have been working?
Will you have been sleeping?
Will she have been studying?
Will he have been cooking?
Will it have been raining?
Will we have been exercising?
Will they have been travelling?
Wh' Questions
Where will I have been working?
Why will you have been sleeping?
Where will she have been studying?
What will he have been cooking?
How long will it have been raining?
Where will we have been exercising?
How long will they have been travelling?
1: Just like with the other perfect continuous tenses (and the future perfect simple), we can use the future perfect continuous to say 'how long' for an action that continues up to another point in the future. The second point can be a time or another action. Generally, we need 'for + length of time' and if we use 'when' or 'by the time', we usually use the present simple.
In April, she will have been teaching for twelve years.
By the time you arrive, I'll have been cooking for hours!
In the same way as with the future perfect simple, we often use the future perfect continuous because we like easy numbers. It's also possible to use the present perfect continuous, but then we get a more complicated number.
I've been working here for 11 months and three weeks. (This is correct, but the time is not an easy number.)
On Tuesday, I will have been working here for one year. (A much easier number.)
2: We can use the future perfect continuous, like the other perfect continuous tenses, to talk about something that finishes just before another time or action (in this case, in the future). It's often used because there will be a result at the second point in the future. (Again, if we use 'when' we usually need the present simple.)
When I see you, I'll have been studying, so I'll be tired.