Learn English – Alternative to “is going to be”

If the subject of your sentence is "I", then Barrie's brief explanation correctly summarizes the essential difference between going to and will. Example:

• I'm going to go shopping after work today.

means that you have already planned what to do later.

• What are you doing after work today? - Haven't thought about it. Maybe I 'll go shopping.

indicates a plan made at the time of speaking.

Of course, you are not always the subject when talking about the future, and the focus may be on predictions rather than plans. In such cases there is no simple rule to follow. For example:

• She's going to have baby (not: She will have a baby)

and

• The baby will be her second child (questionable: The baby is going to be her second child)

Talking about the future is one of the most difficult aspects of English grammar for non-native speakers, and includes many more than the two forms discussed here. I recommend investing in a good reference such as Swan's Practical English Usage, and asking specific questions here on this site if you are not sure which form you need in any given context.

I think this depends on whether you mean to use the phrase with a place or another verb. You can say:

I will be going to America next year / I'll be going to bed soon / I'll be going to the show too.

However if you mean 'to' as part of an infinitive verb then it doesn't work. Compare:

1. I am going to drive to the shop.
2. I will be going to drive to the shop.

(1) makes perfect sense. Although it uses the present tense 'am', the use of 'going' implies it is something that will be done in the future. (2) does not make sense.