Get an unofficial transcript of your grades from the registrar's office.
Find out the exact numerical value of the letter grades you can earn at your school by looking in your student handbook or from the registrar's office. The numerical values of these grades vary by institution, so at Williams College, for example, you can earn an "A+" worth 4.33 grade points while at Cal State Fullerton you can earn 0.7 grade points for a "D-."
Multiply the grade point value of the grade you earned in each class by the academic credit value of that class. So, if you got an "A" in a four-credit course you will have earned 16 grade points.
Add all the grade points you have earned for all the classes you have taken. If you are a full-time student entering his junior year who took an average course load and received mostly Bs, you will probably have earned around 190 grade points.
Divide your total grade points by the total number of credits you have earned and round to two decimal places. The product of that calculation is your grade point average. For example, if you have earned 190 grade points and 62 credits your grade point average is 3.06.
Follow exactly the same procedure if you want to include the grades and credits you anticipate earning this semester or term with the grades and credits you have already earned.