FUTURE TIME

 

Will + infinitive	Be going to + infinitive
A decision at the moment of speaking: Julie: There’s no milk. John: Really? In that case, I’ll go and get some.	A decision before the moment of speaking: Julie: There’s no milk. John: I know. I’m going to go and get some when this TV programme finishes.
A prediction based on opinion: I think the Conservatives will win the next election.	A prediction based on something we can see (or hear) now: The Conservatives are going to win the election. They already have most of the votes.
A future fact: The sun will rise tomorrow.
For promises / requests / refusals / offers: I’ll help you tomorrow, if you like.

Other points about the future:

-We use the present continuous tense for definite future arrangements. Often, it doesn't really matter if we choose 'be going to' or the present continuous. In the following example, there is really very little difference in meaning:

• I'm going to the cinema tonight.
• I'm going to go to the cinema tonight.

-We use the present simple tense in two cases. First, we use it for a timetabled event in the future, like public transport or the start of a class:

• My train leaves at six tonight.
• His class starts at 9am tomorrow.

Second, we use it after certain words, when the sentence has a future meaning. These words are: before / after / as soon as / until / when:

• I'll call you when I get home.
• She's going to study after she finishes dinner.
• Please drink some water as soon as you complete the race.

-We use the future continuous for:

1. A continuous action in the future which is interrupted by a time or by another action.
   I’ll be waiting when you arrive.
   At eight o’clock, I’ll be eating dinner.
   (see the past continuous which is used in a similar way)
2. A complete action in the future that will happen in the normal course of events.
   The Government will be making a statement later.
   Because this talks about something that will happen if everything is as we planned, we often use this tense to ask politely about what someone is going to do.
   Will you be taking your car to the meeting? (=I'm asking very indirectly and politely - perhaps I want to get a lift)
3. To make a guess about the present.
   My mother will be working now. (= I think she is working now, but I’m not completely certain)

-We use the future perfect for:

1. With a future time word, (and often with ‘by’) to talk about an action that will finish before a certain time in the future, but we don’t know exactly when.
   
   By 10 o’clock I will have finished my homework. (=I will finish my homework some time before 10, but we don’t know exactly when)
   By the time I’m sixty, I will have retired. (= I will retire sometime before I'm sixty. We don't know exactly when, but definitely before my sixtieth birthday)