I am going to do it or I will do it, they are the same. In English, expression is formed by two or more words, "going to" is an expression which means "will". Academic English were taught in schools, The teachers will tell you the differences. But, I am not a teacher, I woun't go for the academic rules.

@ Arnold I just learned an academic English term, it is "phrase verb". Would you find the phrase word for "will" ? "will" is not a verb, but it is similar in logic. I think you are talking about the academic English. Most of the exams, text books etc., do not recommend to use the phrase verb. Additionally, there are slangs, idioms, colloquial etc., It may be acceptable in your country, but It is not acceptable in our country. For example: wanna, the word "wanna" is not acceptabe for the teachers, but it is acceptable for the students. Does, wanna and want bear the same meanings? it is another story.

To Erik who disagree :) test yourself - http://www.better-english.com/grammar/willgo.htm Example: Where are you going? I 'm going to visit a customer. NOT- I'll visit a customer. Last one is grammatically incorrect. About your example. My explanation wasn't completely comprehensive and accurate. "You know, I think I'm going to visit my family next week." "You know, I think I will visit my family next week." - here "You know" and "I think"- emphasize that you've just decided to do it. p.s. I don't see and haven't found any reference about Register you said above. I'm sure both are used in formal writing. It's maybe just a style matter. p.s. s. Everything depends on context :)

Thanks for the invitation to see your reply, Arnold. I don't want to belabor the point, since I don't think it will be helpful to Lolifofo. There are reasons for the examples you posted (for instance, when asked where I am GOING, of course I would answer with "I am going to", because the verb has the meaning "to go" to a place here, and not "will"). However, I would stand by my original explanations. Betty Azar, however well known, is incorrect if she said that certain of these are "only" possible. Remember that Betty writes for ESL students. She is giving rules she feels will help ESL learners. She is not giving ALL rules that a native speaker would know. So when she warns you to "only" use "going to" in some situations, she is saying, "If you only use this phrase, you will be correct." This does not mean that if you ever use another phrase, you will be wrong -- only that you must have native skill and understanding in order to do it. I will give a couple of simple examples: Let's say I decided on Monday to buy a car. I bought it. But I can't pick it up until Saturday. My PRIOR PLAN is to pick it up Saturday. I may say the following: "I'm going to pick up the car on Saturday." "I'll pick up the car on Saturday." (will) "I'll be picking up the car on Saturday." (will) There are other ways to say it, as well. Although Betty Azur cautioned ESL users ONLY to use "be going to" with a prior plan, all of the above work (with either "going to" or "will"). One more: My friend Tom and I talked on Monday and made a plan to meet on Saturday. On Wednesday (with a prior plan in place) I can say any of the following: "It's going to be great seeing Tom on Saturday." "It will be great seeing Tom on Saturday." Either works fine, even with the prior plan. I know this, because I am a native speaker. I would be CORRECT to use "going to", and that is usually safe for ESL learners. But I CAN use the others, as well, if I know how and when to do so.

EXAMPLE 2: Let's imagine that Mrs. Thomas teaches a Literature class at a college. At the start of the semester, she hands out a syllabus. The syllabus states that, at the end of the semester, the students must take a final exam. The syllabus states that two hours has been allotted for this exam. Now, three months have passed. It is the end of the semester. Mrs. Thomas has mentioned the exam several times. All students know it is coming. They all know how long they have to take the exam. There is definitely a "prior plan" in place. On the day of the exam, which will Mrs. Thomas say as she hands out the exams? a. "You are going to have two hours to complete the exam." b. "You will have two hours to complete the exam." Again, of course, she will say (b). If she followed Arnold's "rule", she would have said (a). Yet this clearly does not work. Why? Because this is an educational setting, which requires Register 1 language, where only "will" is permitted.