# How to Calculate Grade Scales ••• Jupiterimages/Photos.com/Getty Images

If you have a traditional class grade, you only have to know the total points you earned and the total possible points in the class to calculate your grade (Grade = points earned/points possible). However, if you have a class with a weighted grade scale, you need to take a few extra steps in order to calculate your overall grade in the class.

Identify the grade categories and the weight of each category in the overall grade scale. For example, one teacher may have tests worth 20 percent, homework worth 50 percent, and projects worth 30 percent. You need to know how much each category is "worth" in your grade scale before you can calculate your grade.

Determine your score within each category. Take the total points you earned in that category and divide by the total points possible for that category. For the example above, let's say you earned 80 points on your combined tests with a total possible 100 points in the test category. That means you have earned 80 percent in that category. Now you take your 80/100 (0.8) and multiply it by the weight of that category, which is 20 percent or 0.2. When you multiply 0.8 by 0.2, you get 0.16 or 16 percent. Save that number for later, and repeat this process with your other grade categories.