Understand what is included in the cost of graduate school. This should include tuition, housing, transportation, school fees, books, supplies and any other expenses that are needed during that time.
Decide where you are going to graduate school. Since tuition, books, supplies, housing cost and fees are all incredibly dependent on where you go to school and the city you live in, this will be important to determining the cost of grad school.
Apply for financial aid. The cost of graduate school can be significantly reduced with grants and scholarships. Most grants are based on income, either that of the student's or of the student's parent's if they are living in the same household. Some scholarships are based on need, but there are many that are based on academics, activities, heritage and other more personalized themes.
Take all the expenses per year and minus financial awards per year and it should give you an approximate figure for the cost of attending graduate school per year. Multiply by the number of years you are attending to get a full figure. If you are having a difficult time with this, visit your financial aid office to get a more accurate answer.