Is there any difference between "be going to do sth." and "will do sth."

[weiteng]

Hello folks,
For native English speakers, wherever your from, is there any difference between "be going to do something" and "will do something"?
For me, of course as a foreign tongue for the English language, when I say: "I'm going to get a Coke." That means the action of getting a Coke will happen in a short time, right after I finish this utterance.
Then if I say: "I'll get a Coke". The action of getting a Coke will happen after a certain period of time, and for how long may not be certain.
So is my understanding correct? Can anyone put in your own two cents for my question. Thanks a lot.

[Tdol]

It's often not a question of time with these forms. If I think about it first, then I'll say 'I am going to get a coke', but if I suddenly decide to do it, I will say 'I will get a coke'. 'Going to' is often used for our plans and intentions, but when we decide now, we use 'will'.

[dannyzhen]

Thanks! I've got the meaning of "be going to" and "will". But if I say "it is going to rain", there is no plan or intention. Is it a correct expression? Or should I say "it will rain"? Could you please help to explain it further?

[vil]

I’m not a teacher.

Hi dannyshen,

We use both will and going to to talk about our future action, but there is a clear difference.

Helen’s bicycle has a flat tire. She tells her father.

Helen: My bicycle has a flat tire. Can you fix it for me?
Father: Okay, but I can’t do it now. I’ll fix it tomorrow.

Will: We use will when we decide to do something at the time of speaking. The speaker has not decide before. Before Helen told her father, he didn’t kow about the flat tire.

Later, Helen’s mother speaks to her husband.

Mother: Can you fix Helen’s bicycle? He has a flat tire.
Father: Yes, I know. She told me. I’m going to fix it tomorrow.

Going to: We use going to when we have already decided to do something. Helen’s father had already decided to fix the bicycle before his wife spoke to him.

We use both will and going to to say what w think will happen in the future:

Do you think Laura will get the job?
Oh no! It’s already 3:00. We’re going to be late.

We use going to (not will) when there is something in the present situation that shows what will happen in the future (especially the near future). The speaker feels sure what will happen because of the dituation now.

Look at those black clowds. It’s going to rain. (the clowds are are there now)
I feel terrible. I think L’m going to be sick (I feel terrible now)

Do not use will in situation like those.

The man can’t see where he is going. There is a hole in front of him.

He is going to fall into the hole.

Here the speaker is saying what he thinks will happen. Of coarse he doesn’t mean that the man intends to fall into the hole.

To other situations, we use will

Sue will probably arrive at about 8 o’clock.
I think George will like the present you bought for him.

Regards.

V.

[Raymott]

Originally Posted by dannyzhen

Thanks! I've got the meaning of "be going to" and "will". But if I say "it is going to rain", there is no plan or intention. Is it a correct expression? Or should I say "it will rain"? Could you please help to explain it further?

You can say either:
"I think it will rain today". "I think it's going to rain today".
They mean the same thing, and can be used interchangeably.

Vil has given some good examples, above, of different uses. But in most cases, "will" and "going to" mean the same thing.

As far as getting a Coke is concerned, if you're going to do it immediately, you can use the present tense: "I'm getting a Coke".