The formula to calculate the curved grade is:
\[ \text{SG} = \frac{\text{OG} \times 100}{\text{MG}} \]
Where:
Scaling a grade, or curving a grade as it’s often referred to, is the process of changing the scores of a test to represent the performance of the overall class on a 100-point scale. This most often means that the highest grade scored is scaled to 100, and any score under that is scaled based on that highest grade.
Teachers curve grades because they want to increase the overall test grade average of the test. There can be several reasons for this, one of them being if a test they design ends up being too difficult and the whole class gets bad grades, they want those grades brought up so the students aren’t failing.
Let's assume the following values:
Using the formula:
\[ \text{SG} = \frac{75 \times 100}{90} = 83.33 \]
The Curved Grade is 83.33%.
Let's assume the following values:
Using the formula:
\[ \text{SG} = \frac{85 \times 100}{95} = 89.47 \]
The Curved Grade is 89.47%.