The Future: Will, Be going to, Present Continuous, Present Simple

Will

• Will is the most common way to refer to future time.
• We use will / won’t + infinitive to make confident predictions about future events or situations.
  • This’ll be interesting.
  • She won’t say no! Not to a good-looking guy like you!
• We use will / won’t + infinitive for things we decide quickly at the moment of speaking.
  • I’ll come round to your house at about 10 am, then.
• We use will / won’t + infinitive to make offers or promises.
  • I’ll let you know as soon as it’s ready.
• We usually use will in a more formal style, e.g. in invitations, public notices, etc.
  • The wedding reception will begin at 8:30.

Be going to

• We use be going to + infinitive for the future when there is present evidence that something is going to happen, when the event is already starting / starting very soon, and (particularly in informal style) for present plans / intentions for the future.
  • It looks like he’s going to give his speech.
  • I’m going to ask her to marry me.

Present Continuous

• Use the present continuous to talk about already fixed plans / arrangements.
  • Are you giving a speech? (asking if this has already been arranged)
• We use will or be going to + infinitive, not the present continuous, for predictions about events which are out of your control.
  • It’ll take / ’s going to take a couple of hours to get there. NOT It’s taking …

Present Simple

• We usually use the present simple for known facts about the future or future events which are part of a fixed timetable.
  • The wedding is at 2.
  • What time does your train leave tomorrow?

Will or Be going to

• We can often use either will or be going to + infinitive for facts / predictions about the future.
  • Christmas Day will be / is going to be on a Friday next year.
• We usually use will (won’t) + infinitive to say things about the future based on personal opinion / beliefs. We usually use be going to + infinitive to make predictions when there is clear outside evidence.
  • She’ll have lots of children. (= I know she wants to have lots.)
  • She’s going to have a baby. (= She’s already pregnant.)

Will, Be going to or Present Continuous

• We can often use either be going to + infinitive or the present continuous, not will, for present plans / intentions / expectations for the future.
  • I can’t meet you after work tonight. I’m going to see / I’m seeing a film with Kamala. NOT I’ll see a film …
• If we are considering a plan and are still not sure, we sometimes use will after I think.
  • I think I’ll leave about 11:30.
• After words like when, after, before, as soon as, if, unless and until we use the present simple (or the present perfect), not a future form, although we are talking about future time.
  • When you arrive home, you can tell me about your journey. NOT When you will arrive …

Source: Active Grammar, Level 3, Mark Lloyd and Jeremy Day, CUP, 2011 (With Ramrowriter’s adaptation where necessary)