How to Grade on a Curve & Why Is It Needed?

How to Grade on a Curve & Why Is It Needed?
Table of Contents
  1. How to Grade on a Curve & Why Is It Needed?
  2. Method 1 - Mathematical curving approach
  3. Method 2 - Use a flat-scale formula
  4. Method 3 - Use a bottom limit to define an F
  5. Method 4 - Use a bell curve
  6. What is the purpose of curve grading?

It may sometimes happen that a teacher needs to curve the grades by assigning scores to different academic tasks based on the performance of the whole class. Why is that needed? And what are the main features of grading curves? Everything is easy - when curving grades, a professor can clearly see the general class performance and understand whether the test was of the appropriate difficulty. What is more, it is also important for the student to know how to grade on a curve. The curving method allows a student to recoup some points they lost on a particular assignment. So what is the easiest curving formula?


Method 1 - Mathematical curving approach 

This is one of the most widely used curving methods, being very easy to follow. Start with assigning 100% to the highest score you have. The value of other grades is calculated based on the “100% top level” you have just identified n the curve. As a result, all the scores will be higher since the pre-set 100% excellent score is different from how it was initially. If done correctly, the method will boost your scores greatly.

  • Example - you have 90% out of 100% for the Biology test. The calculation should go as follows: 100 - 90 = 10, which means you need to add 10 to each and every grade of yours. Thus, you will adjust all your scores to the hypothetical “perfect” score.

Another good thing about this method is associated with its flexibility. You can apply this formula to absolute values. The logic of calculations remains the same.

Method 2 - Use a flat-scale formula

It is another easy and fast method of curving, which is especially useful in case there was one difficult assignment and many students have failed to complete it correctly. The calculation formula is very similar to the first one and is based on adding a pre-set value to all the scores, although you do not have to set up 100% for the highest grade. It is you who decides on the value to add.

  • You can add 10 or 5 to all figures; thus, there might be no 100% in the point range. At the same time, there is also a possibility of scores that exceed 100%. That’s why it is so important to decide on the benchmark.

Method 3 - Use a bottom limit to define an F

It may happen a student has failed a test scoring 0 despite the fact that his academic performance has always been satisfactory. As a result of this academic assignment, he might get a failing value, which is unfair. To prevent this situation from happening, many teachers set a bottom limit for any failing value that is higher than 0 points. Thus, the increase the final value.

  • Example - a student fails the test and gets an F for it; consequently, his final grade is less than 50, which is a failing score. Fortunately, it is still possible to make his average score higher. To do this, it is only necessary to set a lower limit on failing score, for example, 40%. As a result, the new GPA of a student will be 63,3%, which is no F anymore.

Method 4 - Use a bell curve

This method implies that you find the average value and then adjust all other (higher/ lower) points to it. Let’s assume the average point is 66%, which you set up as a C. Thus, to separate low from high grades, you just need to either add or deduct a particular amount of points; you can decide on this amount yourself. Let’s say, you decide to use 12 for this purpose.

  • As a result, you get 66 + 12 = 78, which is a B; and 66 - 12 = 54, which is a D.

As a result, you objectively raise the score level gradually without going extreme.


What is the purpose of curve grading?

By following this approach, you can fix the academic performance or increase the average score. If you do not want to apply complicated formulas, there are still some alternative approaches for you to follow. Here are some of the solutions :

  1. Provide the possibility to re-do assignments/ tests;
  2. Exclude excessively complex tasks from the program;
  3. Assign easy-scoring tasks to your students if they fail with a complicated test.

Regardless of the way you follow, it is always important to keep an eye on the fairness of the average grade since it may sometimes need some fixing from both the student and the teacher. The best approach would be to adjust your strategy to a particular case.