“Be going to” is a grammatical construction in English that is used to refer to various types of future occurrences. “Will” is a modal verb used in the future simple tense to talk about the future.

Here, I explain the differences between the two with regard to their timeline and how they are used in English.


Overview

Be going toWill
DecisionsMade before time of speaking.Made during time of speaking.
PredictionsBased on current evidence.Based on personal opinion.
Future events that are certain to happen or future facts.
Express something that is about to happen.

Differences

As a modal verb, “will” has other uses as well but I’ve narrowed this list to the differences that relate to the future.

1. When a decision is made.

For “going to,” the decision is made prior to the time of speaking.

  • “I‘m going to cook spaghetti tonight.”
  • “We‘re going to the cinema this weekend.”

For “will,” the decision is made at the time of speaking.

  • “I‘ll get the spaghetti please.”
  • “Let’s go out this weekend. We‘ll have dinner and watch a movie after.”

* Please note: Using either “going to” or “will” only reveals when the speaker has made a decision. So it is possible to use them incorrectly (and get away with it) because when a decision is made is not always clear to the listener.

a. In first conditional sentences.

The First Conditional is usually used to describe things that are likely to happen in the future. Both “going to” and “will” can also be used here to express when a decision was made.

* Please note: There are other conjunctions that can be used with the First conditional. “If” is the one in focus here.

  • “If I get home early, I‘m going to call my mom.”
    This implies he made a decision to call his mom prior to the time of speaking.
  • “If I get home early, I‘ll call my mom.”
    This implies a spontaneous decisions at the time of speaking.
  • “If he gets promoted, he‘ll buy a new car.” 
  • “If he gets promoted, he‘s going to buy a new car.”
    This implies a spontaneous decisions at the time of speaking.
  • 2. Predictions: Evidence-based or guesses.

    When it comes to predictions, “will” and “going to” are often interchangeable.

    • “I think the weather will/is going to be nice later.”
    • “Do you think we will/are going to be able to get tickets?”

    The difference is that “going to” is based on current evidence, whereas “will” is more of a guess. So use “going to” if you have any evidence to back it up.

    • “The weather forecast says it‘s going to rain all week.”
    • “I have a feeling it‘ll rain later.”
    • “I just watched the news. Looks like prices are going to continue increasing.”
    • “If we don’t vote for the party, prices will continue to increase.”
    3.   With “will” – To refer to future facts or events in the future that are certain.

    Generally, “will” is used when we refer to things in the future that we think are certain.

    • “The sun will rise tomorrow.”
    • “I‘ll turn 35 next month.”
    • “Because of the delays, the project won’t be finished by the end of the year.”

    “Going to” is not typically used in in this way (prior decision or prediction based on current evidence), but sometimes we can use them interchangeably to express something similar—albeit with subtle differences.

  • “The sun is going to rise tomorrow.”
    This is not similar at all. “Going to” personifies the sun by emphasising that it made the decision to rise. This expression is sometimes used to encourage people to get through a difficult time. This is similar to, “Tomorrow is a new day.”
  • “I‘m going to turn 35 next month.”
    Based on my date of birth, this is going to happen. Otherwise, “will” and “going to” can be used interchangeably here.
  • “Because of the delays, the project is not going to be finished by the end of the year.”
    This can due to be prior decisions made or predictions due to the delays. I’d also say this is interchangeable.
  • 4. With “going to” – To express something that is about to happen.

    Based on what is happening at the moment (evidence), we can use “going to” to express something that is about to happen.

    Here, there is a feeling of immediacy that doesn’t have the same impact with “will.”

  • “The bomb‘s going to explode!”
    This sounds like the bomb is about to explode very soon or immediately.
  • “The bomb will explode!”
    This sounds more like a future fact. It will definitely explode but maybe not immediately.
    • “Get off the table now or it‘s going to break!”
    • “That cyclist is going to hit the car!”

    Original post: 10 October 2020

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