I am going to do something= I have already decided to do it, I intend to do it:
- 'Are you going to eat anything?' 'No, I'm not hungry.'
- A: I hear Sarah has won some money. What is she going to do with it?
B: She's going to buy a new car. - I'm just going to make a quick phone call. Can you wait for me?
- This cheese smells horrible. I'm not going to eat it.
I am doing and I am going to do
We use
I am doing (present continuous) when we say what we have
arranged to do - for example, arranged to meet somebody, arranged to go somewhere:
- What time are you meeting Ann this evening?
- I'm leaving tomorrow. I've got my plane ticket.
I
am going to do something = I've decided to do it (but perhaps not
arranged to do it):
- 'Your shoes are dirty.' 'Yes, I know. I'm going to clean them.' (= I've decided to clean them, but I haven't arranged to clean them)
- I've decided not to stay here any longer. Tomorrow I'm going to look for somewhere else to stay.
Often the difference is very small and either form is possible.
You can also say that 'something is going to happen' in the future. For example:
The man isn't looking where he is going.
He is going to walk into the wall.
When we say that 'something is going to happen', the situation now makes this dear. The man is walking towards the wall now, so we can see that he is going to walk into it.
Some more examples:
- Look at those black clouds! It's going to rain. (the clouds are there now)
- I feel terrible. I think I'm going to be sick. (I feel terrible now)
- The economic situation is bad now and things are going to get worse.
I
was going to do something = I intended to do it, but didn't do it:
- We were going to travel by train, but then we decided to go by car instead.
- Peter was going to do the exam, but he changed his mind.
- I was just going to cross the road when somebody shouted 'Stop!'
You can say that 'something
was going to happen' (but didn't happen):
- I thought it was going to rain, but it didn't.
