1. Open up the calculator:
http://sro.mmosite.com/x/
2. Select your character's level in the "Current Character Level" combo box. For example, if you have a current character level of 10 you will select "10" for the current character level.
3. For each of the masteries that are listed, select the current level for each of them that your character has. For example, if you have Bicheon Mastery currently at level 9, you will select "9" for that mastery. If you have other masteries, you will select their levels as well in the correct section.
4. Go though each of the masteries that you have SP in and fill in the level of any skill you already have. For example, if you have Illusion chain at level 1, you will place a "1" there, not a "2". Do this for all the skills your character has for all of the masteries that you are using.
5. Once you are done, the left side should reflect what your character currently has. The masteries and skill levels should match your current characters.
6. The right side is the same, except you fill in what you want your character to be. For example, if you plan to get your character to level 30, you will select "30" for the "Planned Character Level" combo box.
7. Next you will go though and select the final levels of all the masteries you will be using. For example, if you want to have your Bicheon Mastery at level 20, you will select "20" for it.
8. Now you go though and select all the skills you wish to have as well as the final level of those skills. For example, let's say you want to have Illusion chain at Level 4, you will place a "4" there.
9. When you are all done, the right side will reflect your "final character". Hit Calculate in the top right corner. The information box will be updated.
"Required EXP" - Is the total amount of EXP you need in addition to get to your final level.
"Required SP EXP" - Is the total amount of ESP that you need to get all of the SP you need. 400 SXP == 1 SP
"Required SP" - Is the total amount of SP you need for your final character, 1 SP == 400 SXP
"Mastery Level" - Is the total mastery level for all skills. Since 300 is the limit it will tell you how much you have left to allocate to other levels of skills.
The point of this calculator is to let you know how you need to pace yourself to get your final build. Take a look at
this thread to see how much SP you get per level with a certain gap. Hope it makes better sense now!