How to Calculate School Grades by Percentage

How to Calculate School Grades by Percentage
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Nothing is more stressful than worrying about your school grades. How well do you need to do on your final exam to pass the class? How do you even work it out? Calculating your school grades by percentage means combining the “weighting” percentage for each part of the class (or each assignment) with your scores to determine your final result, and you can do this easily with some straightforward math.

Scores and Weighting

The reason people look for a school percentage calculator or similar tools is because of the important distinction between your score on an assignment and the weighting of that assignment. You might have received 20/20 on an assignment, but that doesn’t mean you get 100 percent for the whole class if there are five assignments in total, for example. The weighting tells you how much each individual score matters to your overall mark in the class, and this is usually expressed as a percentage.

You can understand this intuitively if you look at the possible scores for each assignment and the percentages of the total. The scores might not add up to 100 or anything that your teacher would feasibly give you as a final mark, but the weightings will add up to 100 percent.

Converting Percentages to Decimals

An important part of the process of calculating your final score from your original grades is converting the weights for each assignment into decimal forms. Thankfully, this is really easy to do. All you need to do is take the percentage amount and divide by 100, equivalent to moving the decimal place two spots over to the left. So 85 percent is 0.85, 50 percent is 0.5, 23 percent is 0.23, and 100 percent is 1.

Calculating Your Score

The process for calculating your total score from the individual results and their weightings is simple: Multiply the (decimal version) of the weighting by the score for that assignment, then add up all of the final results.

For a concrete example, imagine you have four assignments for a course and a final exam, where each assignment is weighted at 15 percent, and the exam is 40 percent, with the maximum possible score on each being 100. Your scores on the assignments are 70, 83, 77 and 90, and for the final exam you got 65: What is your final score?

For the assignments, you multiply the scores by the decimal form of 15 percent, i.e. 0.15, giving 10.5, 12.45, 11.55 and 13.5. For the exam, you use 0.4 as the decimal form of 40 percent, and then multiply this by 65 to get 26. Your total score is then all of these added together: 10.5 + 12.45 + 11.55 + 13.5 + 26 = 74.

Averaging Evenly Weighted Scores

If your scores for a class are all weighted the same, the process is much simpler: You just take the average of all of the results to find the final score. In other words, add up all the individual scores and then divide the result by the total number of scores. For the scores in the previous example, 70, 83, 77, 90 and 65, this gives:

\begin{aligned} \text{Average score} &= \frac{70 + 83 + 77 + 90 + 65}{5} \\ &= 77 \end{aligned}

Online School Percentage Calculator

Although the process for calculating your school grades by percentage isn’t especially difficult, there are many online tools (see Resources) that can make the process much simpler for you.

To use these, you input the grade for each assignment (or part of the class) and the weighting for it, and then hit the “Calculate” button (or something similar) to find your final mark. Some of these also allow you to work out what grade you would need on a final exam or assignment to hit a certain boundary (e.g. to get an A overall).

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