Hi! I'm 15 and I'm actually from the United States, and this is not really a popular thing over here. I'm probably going to Europe for a year next year and I'm interested in trying this. Could someone give me an idea of what grade I would be in?
These are the songs I'm playing at a piano competition next February:
Sonata in C, K.545, First Movement - Mozart
Waltz in A Minor - Chopin
Sonatina in C - Pescetti
Arietta (12,1) - Grieg
Habanera - Bizet
I'm also playing a few of Bartok's Romanian dances.
Approximately what grade are these and what grade would I probably be overall?
I'm really sorry...I'm pretty unfamiliar with this whole thing!:)

Your level of playing should depends on how well you play the piece rather how difficult the piece is. With the ABRSM exams you will also reach the standard of the required scales, sight-reading and aural tests.

However, the pieces you have quoted are roughtly grade 5 in ABRSM standard.

grade 5 would be nice
you cant get higher grade exam if you dont have grade 5 theory`s certificate

Unless you use a different exam board.

how about if we have grade 5 theory's certificate but we dont have grade 5 practical? can we go ahead for grade 6, 7, 8?

Yes, as long as you have the theory, that is fine.

Is level 5 good? I've always wanted to major and get a degree in Piano (I don't know how all of that works in the UK) but level 5 seems kind of low to do that. For someone who wants to go into piano, is level 5 low for a 15 year old? I won't be offended...I just want to know if I am being practical or not.

Yes, realistically probably a bit low but it all depends on your standard of playing at that level. Here in NZ the level of pieces some people play ( and play very well ) is stunningly and frighteningly high.
For example in the recent Auckland Piano Scholarship Comps the two 13-15 yr classes were won with someone playing Rachmaninov's Prelude in G minor Op23 No 5 and the other one by a boy playing the 1st movt of Sonata in Bb Op 83 by Prokofiev.
These are both pieces that would challenge most professional pianists let alone students and both boys played virtually faultlessly.
In this country the increasing number of Asian students has made the standard higher ( can only be a good thing) and entry to Uni. to study music much harder.
However you have another couple of years and anything is achievable with hard work!
Go for your dream.

I think that grade 5 at 15 is about right for most 'average' people who mybe began learning at 7 or 8.
Certainly there are the high flyers who are way ahead of this by that age (or even younger) but if you take grade 5 as being somewhere in the region of an A - C grade in GCSE (taken in the UK at 16) then it is a reasonable point to be at that age and with that many years learning.

But megan 89 doesn't want to be an average person

She says "I've always wanted to major and get a degree in Piano "

So she will need to be well above average to do that.

I wasn't implying grade 5 at 15 wasn't a creditable achievement - indeed it is, but in my opinion she will need to move significantly further to achieve her stated aim by 18.

And I wish her the best of luck

The songs you are playing is not the only factor used in determining your grade. For instance, how many years have you been training? In addition, your repertoire only counts as 90 pts. in your final exam. Your sight reading ability, technical ability, and aural skills also have to be taken in consideration. While all things improve with practice, I believe you should do what is most comfortable for you.

As said earlier, you need to take Grade 5 Theory to do Grade 6 Practical in any instrument, and the theory exam will probably take you a few months to prepare for, depending on your testing locations and times (I understand you live in the US).

In addition, if you are referring to "Waltz in A Minor, by Chopin" as Grande Valse Brillante (Op. 34, No. 2) in the key of A minor, I didn't start that piece until grade six. However, most of my Bartok studies were around grade five. But again, there are more things to consider than repertoire.

You should definitely consult your teacher about this. Right now, you should definitely take what is most comfortable for you. If you progress well, many people take two grades in one year. Time is definitely a considerable factor - if you want to go for the reach, you have to be prepared.

Best of luck!