Like many of the languages related to it, English has more than one way to talk about actions in the future. The first is the future tense, which is the ‘will’ future (and the closely related ‘shall’). The other is the ‘going to’ future. If you are not familiar with the “going to” (present progressive) and ‘will’ (simple future) form of verbs, I would recommend you read A Review of Tenses In English.
The will future is formed by using the word will followed by the base form of a verb (the infinitive without the to in front) or an aspect (continuous, perfect) in the positive; in the negative, will not or the contraction won’t is used. For example:
Tomorrow I will go outside. – will followed verb in base form -> future simple
In five years she will have become a doctor. – will followed by perfect aspect -> future perfect
I will be having a drink after the exam tomorrow. – will followed by progressive aspect -> future progressive
I will have been having a massage for three hours when you arrive. – will followed by perfect and progressive aspects -> future perfect progressive
I won’t be there tomorrow. – won’t followed by verb in base form -> future simple
Going to Future
The going to future is formed by using the auxiliary (‘helping’) verb to be conjugated in the present simple tense followed by going to. In the negative, the going to is negated with not, so the result is not going to.
Tomorrow I am going to go outside.
An additional note: apart from the simple future, the other future aspects (perfect, continuous, perfect continuous) usually use the will or shall future:
Tomorrow I am going to be going outside… – this is long and means the same thing as replaced with: Tomorrow I will be going outside.
To be a bit more confusing, some English-speaking countries (the UK, for example) use the word shall to also indicate the future. It is formed the same way as the will future and is also negated by the word not, forming shall not or shalln’t (the contraction is more common in speaking than it is in writing). This use is typically reserved for the first person (I, we) but can also be used for second (you) and third persons (he/she/it) as well. For example:
Tomorrow I shall go outside. – ‘shall’ followed verb in base form -> future simple
In five years she shall have become a doctor. – ‘shall’ followed by perfect aspect -> future perfect
I shall be having a drink after the exam tomorrow. – ‘shall’ followed by progressive aspect -> future progressive
I shall have been having a massage for three hours when you arrive. – ‘shall’ followed by perfect and progressive aspects -> future perfect progressive
I shalln’t be there tomorrow. – ‘shall’nt’ followed by verb in base form -> future simple
In other countries (most notably) the US, this practice of using shall for the future has been declining for a long time. Instead many speakers will use should. For example:
I should be having a drink after the exam tomorrow if you want to meet me.
So there are three ways to form the future, but how do you know when to use one versus the others? Originally shall was the default go-to future form as shall was considered the polite form of phrasing a sentence. At this point will was used primarily for commands. Over time this has changed. Today part of the answer to that question depends on what type of English you are learning. If you are learning American English, it is unlikely that you will hear the word shall except in documentaries, historical dramas or legal texts such as contracts. In those cases, it is used to show that they are speaking more formally. In everyday use, the word shall is dying out, especially in the US but also in Canada. For those who are learning another type of English (British, Australian, New Zealand, Indian, etc.), the word shall is still used on some occasions, although not as often as it was in the past.
Uses of will future
The will future is the most robust of the future forms because it can be used in a lot of ways. For example:
- To predict a future event
It will rain tomorrow.
- to express a spontaneous decision with I or We (you can’t make spontaneous decisions for other people!)
Don’t worry about it. I’ll pay.
- to express willingness/unwillingness
He‘ll carry the bag for you.
He won’t carry the bag for you.
- To give orders
You will go to bed right now young man!
- To make an invitation as a question
Will you marry me?
If you are learning a type of English that does not use ‘shall’, you can skip the next section.
Uses of shall future
For those learning a type of English that still uses shall. There are a few more considerations. For the uses listed for the will future, the word shall can be used almost interchangeably to mean the same thing. For example:
He shall carry the bag for you. = He will carry the bag for you.
He shalln’t carry the bag for you. = He won’t carry the bag for you.
However, there are two additional uses. Because the word shall is considered more polite to use than the word will, it is often used in questions. For example:
- to make an offer/suggestion
Shall we go for lunch? Shall I pay?
- to ask for advice or instructions
What shall I tell the boss about this money?
Reminder: In types of English that no longer use shall, the modal verb should is usually used instead: Should we go for lunch?
Uses of Going to future
In the simple future, going to can replace will. For example:
Tomorrow I am going to the station.
Tomorrow I will go to the station.
Both sentences are grammatically correct, but be careful! There is a difference in meaning. If you remember back to the differences between using the present to talk about the future tense and the future tense, you will remember that the going to future is used for definite events that will in the near future. I am going to the station means that you have a set plan that you have arranged. I will go to the station means that something about it not certain, for example, it hasn’t been planned.
In short, the going to future is for things with prior planning or for set plans in the future. The will and shall futures are used for spontaneous decisions, offers, threats, refusals and promises.
Are there any fields where you can interchange will/shall and going to and have them mean the same thing? Yes there is! Both can be used for predictions, such as in the following sentences:
Tomorrow it will rain.
Tomorrow it is going to rain.
Here we see that someone is making the prediction that it is going to rain. In this case, both sentences mean the same thing. A native speaker might subconsciously use the ‘will’ future to mean that it is less likely to happen (or they are less sure) and the ‘going to’ to mean it is more likely (or more sure that it will rain) but this may also not be the case.