Gundam Grade

So you probably heard a lot about HG, MG, PG, SD, here is a more detailed explanation about them.

Gunpla comes with different scales, 1/144, 1/100, 1/60. And some time there are 1/48 and larger models, but the first three and SD models form the mainstream.

SD

SD stands for Super Deformed. They are smaller than 1/144 scale models (in most cases), and usually comes with less pieces. If we don't take any customization in count, you should probably be able to put up a SD in half an hour to one hour, depending on how carefully you work on it. SDs are usually the cheapest ($10~$15), sometimes you can even get a deal at $2.

HG

HG stands for High Grade. HG has more pieces, and the models are more detailed and colorful. HG usually comes in 1/144 scale. The good thing about HG is that they cover a lot of selection of models (Mobile Suits, Mobile Armor), and they are not very expensive, usually around $20. For bigger models and special editions, the price may go up to $60.

Both SD and HG are good for starters :)

RG 

There is another grade at 1/144 scale, RG, Real Grade. RGs are even more detailed than HG, but still below MG. The biggest difference is that RGs start to have inner structures below the armor parts. RGs usually cost you around $35, so they are good for those who have already tried a few HGs and want to have a taste of a better grade. But RGs only come with a limited selection of models (RX-78, Zaku-II Red, Zaku-II Green, Aile Strike and Freedom at the moment).

MG

MG stands for Master Grade. MG scales at 1/100. MGs are even more detailed of course, with inner structure. It is a little bit more expensive than HGs. Usually 2x to 3x of the price of HG. They are the main product Bandai is focusing on.

PG

PG stands for Perfect Grade, 1/60 scale. They are really awesome and really expensive. Period.

There are also some other grades, I won't go into the details, but just list them here.

Mega size, 1/48.

MEGA

Jumbo size, 1/35

Jumbo

Life size, 1/1

1:1

About No Grade. Sometimes on gundam web stores you will notice some models marked as No Grade, or does not have a grade specified. In that case, they are usually about the quality of HG, but come with bigger size.

AG, 1/144. Tool free.

Gaging, 1/144 ? Not very sure :/

Speed Grade, 1/200

When buying online, pay attention that there are also some models are pirate from Asia. Some of them have pretty good quality, most of them not. Some people love to do customizations on those because they are relatively cheap. But not recommended for n00bs(like me).

There are also a lot of things not covered here. But you'll know when you know :)