How to Calculate Percentage of Marks – Step-by-Step Guide

A percentage is a way of expressing a number as a fraction of 100. It helps to compare values easily, no matter the scale. In education, percentages represent marks because they provide a clear and standardised way to evaluate a student’s performance across subjects and exams.

Let’s understand this with an example of Yash, a student who appeared for five subjects in an exam. Each subject has a maximum of ₹100 marks.

To calculate his overall percentage:

Total Marks Obtained = ₹80 + ₹70 + ₹65 + ₹75 + ₹60 = ₹350
 

Total Maximum Marks = ₹500
 

Overall Percentage = (350 ÷ 500) × 100 = 70%

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Basic Formula for Calculating Percentage of Marks

Let’s say Ananya appeared for three tests in different subjects. Her obtained marks and the total possible marks for each subject are given below:

Step-by-Step Method to Calculate Percentage

Let’s say Sana appeared for five subjects in her annual exam. Now, let’s look at each step to calculate her overall percentage.

Step 1: Add All Obtained Marks

Total Obtained Marks=72+88+81+65+74=380

Step 2: Add Total Possible Marks

Total Maximum Marks=100+100+100+100+100=500

Step 3: Apply the Percentage Formula

Percentage=(380÷500)×100=0.76×100=76%

Step 4: Round Off if Needed

76% is already a whole number in this case, so no rounding is needed.
 

But if Sana had scored 382 out of 500:

(382÷500)×100=76.4%

She could round it to 76% or 76.4%, depending on how precise the result needs to be.

Tips for Quick Mental Calculation

Tip 1: Use Common Fractions as Percentages

Shortcuts you can remember for easy calculation:-

Example: Raj Got 15 Out of 20 Marks

Let’s try to estimate his percentage quickly.

15÷20=3÷4

Since ¾ = 75%, Raj scored 75%, no calculator needed!

Tip 2: Find 10% First, Then Multiply or Scale

This is great when you're dealing with tricky numbers.

Example: What's 30% of 250?

Step 1:
 

Find 10% of 250:

10%=250÷10 which is equal to 25

Step 2:

Multiply by 3 (since 30% is 3 × 10%):

30%=25x3=75

So, 30% of 250 is 75.

Why This Helps

• Saves time during exams or while checking marks.
• Reduces dependency on calculators.
• Builds strong mental math skills.

Common Mistakes to Avoid in Percentage Calculations

Calculating percentages is straightforward when you follow the correct steps. However, there are a few common errors that students often make. These mistakes can lead to inaccurate results and confusion when interpreting marks or grades.

Below are the most common mistakes, along with clear explanations and examples. Identifying these errors early helps in building a strong foundation in percentage-based calculations. Being careful with basic operations like division and multiplication ensures greater accuracy and confidence during exams.

Mistake 1: Dividing Total Marks by Obtained Marks

Some students mistakenly divide the total marks by the obtained marks instead of dividing the obtained marks by the total marks. This reverses the relationship and results in an incorrect (mostly exaggerated) percentage.

Example:
 

Let’s say Priya scored 45 marks out of 60 in a subject.

Correct Calculation:

Percentage=45÷60x100=0.75x100=75%

Incorrect Calculation (Common Mistake):

60÷45x100=1.33x100=133.33%

Why This is Wrong:

A student cannot score more than 100% without extra credit. This mistake happens because the order of division is reversed.

Mistake 2: Forgetting to Multiply by 100

Sometimes students calculate the ratio correctly (obtained marks divided by total marks) but forget to multiply the result by 100 to convert it into a percentage. This leads to a decimal answer that is not in the correct format.

Example:
 

Suppose Rohan scored 32 out of 40.

Correct Calculation:

32÷40=0.8

Percentage=0.8x100=80%

Common Error:

Writing “0.8%” instead of 80%.

Why This is Wrong:

The result 0.8 is a decimal (or 80 out of 100 in percentage terms). Forgetting to multiply by 100 causes the result to appear 100 times smaller than the actual value.

Calculating Cumulative Percentage Across Terms

In many academic settings, especially in schools and colleges, students receive marks across multiple terms, semesters, or examinations. To evaluate overall academic performance, calculating the cumulative percentage is essential. This gives a complete picture of a student’s progress over time.

How to Calculate Cumulative Percentage

Instead of averaging term percentages (which can be misleading if total marks vary), follow these steps:

1. Add up all the obtained marks from every term or semester.
2. Add up the total maximum marks across those same terms.

3. Apply the formula: Cumulative percentage=(Total obtained marks/Total maximum marks)x100

    

Cummulatove percentage=(800÷1100)x100=72.73%

Why This Matters

Simply averaging percentages from each term (e.g., 76% and 70% = 73%) does not consider the difference in weight or total marks. The cumulative percentage reflects the actual performance weighted by each term’s total marks, making it the most accurate method.

Mistake 3: Averaging Percentages Instead of Raw Marks

Students sometimes try to find an overall percentage by averaging individual subject percentages instead of using total marks. This only works if all subjects have the same total marks. If the subjects have different maximum marks, this method gives an inaccurate result.

Incorrect Example:
 

Let’s say a student gets:

• 90% in Science (out of 100 marks)
• 70% in Mathematics (out of 200 marks)
  
  Also Read - How to Calculate Average Percentage – Step-by-Step Guide
  
  

Averaging the percentages:

90+70÷2=80%

This seems correct, but it’s misleading because the subjects have unequal weight.

Correct Method (Using Raw Marks):

• Science: 90 marks out of 100
• Mathematics: 140 marks out of 200

Total Marks Obtained: 90 + 140 = 230
 

Total Maximum Marks: 100 + 200 = 300

Percentage=230÷300x100=76.67%

So, the correct overall percentage is 76.67%, not 80%.

Why This is Important:
 

Always use the actual marks when calculating overall performance to ensure fairness and accuracy, especially when subjects carry different weightage.

Being aware of these mistakes and taking a moment to double-check your steps can help you avoid errors and ensure your percentage calculations are accurate.

Conclusion

Calculating the percentage of marks is a straightforward but important process in academic evaluation. To find the percentage, one must divide the total marks obtained by the total maximum marks and then multiply the result by 100. This method standardises scores across different subjects and exams, making it easier to compare performance. 

It is essential to follow the correct order of division, obtain marks divided by total marks, and remember to multiply by 100 to express the result as a percentage. Avoiding common mistakes, such as reversing numbers or averaging percentages without considering subject weight, helps ensure accuracy. With practice and the use of simple tricks like estimating through fractions or scaling from 10%, anyone can calculate percentages quickly and confidently.

FAQ’s

1. How do I calculate the percentage of marks in an exam?
Divide the obtained marks by the total marks, then multiply the result by 100.
Formula: (Obtained Marks / Total Marks) × 100.

2. Can I calculate a percentage without a calculator?
Yes, you can use basic division and multiplication. Estimating using fractions like ½ = 50% or ¾ = 75% also helps.

3. What if all subjects have different total marks?
Add all obtained marks and all total marks, then use the formula: (Total Obtained / Total Maximum) × 100.

4. Is averaging subject percentages correct?
Only if all subjects have the same total marks. Otherwise, calculate the overall percentage using the total marks.

5. Why is multiplying by 100 important in percentage calculation?
Multiplying by 100 converts the decimal result into a percentage format, making it easier to interpret.

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