Percentage Error And The Method To Calculate It

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antoine dautry 05A kdOH6Hw unsplash

Percentages are the most widely used criteria for calculations. It is the easiest method to convey our observations in any field which involves numbers. The use of percentages facilitates comparison in the simplest manner. 

For example, my daughter scored 23% higher this time than her last attempt. Also, all the growth the corporate sector makes in an annual year is calculated in percentages.

Not only that, it is widely used to forecast results in any field. When companies prepare their annual data, their targets for the next financial year are calculated in terms of percentages. When students set goals for themselves, it’s usually the percentage data they are most comfortable with. 

For example, I will improve my performance in the next semester by at least 20%.

When predictions are made, it’s very obvious that they would be wrong sometimes or the other. A certain company might grow double than it predicted for a particular financial year. A certain student might not be able to make it to the institution of his choice because the expected percentage improvement in his score couldn’t be reached.

In all the above cases, it becomes imperative to calculate the percentage error. It’s indeed very important to know approximately how much error has been made in forecasting. Per cent error lets you see how far off you are in estimating the value of something from its exact value. 

Finding percentage errors helps us to improvise our data, and we can target our results in a more effective manner.   

How to Calculate Percent Error:

  • Calculate the difference between your expected value and the actual value.
  • Calculate the quotient of the difference between values calculated in the first step and the exact value.
  • Multiply the above-obtained quotient value to 100.
  • The above-calculated value is your required percentage value. Attach the percentage notation to this value.

The formula for calculating percentage error

With regard to the results obtained using the above formula, it’s important to note that if the per cent error is close to zero, then our approximation is very close to the actual value. This formula is very important to determine the precision of your calculations.

Two cases may arise in the above calculation :

  • The exact value in a particular case is greater than the expected value. In this case, the percentage error appears to be positive.
  • The exact value in a particular case is much lower than the approximate value. In this case, the percentage error appears to be negative.

Usually, in most disciplines, the sign of the per cent error is not considered except in chemistry and some other sciences where it is customary to keep a negative sign.

Importance of the concept of percentage error 

  • In calculating national statistics, the percentage error calculation is crucial for policymakers to curb the ill effects of wrong policies resulting from the erroneous data. 

Data related to various departments of any country impacts the economic decisions and welfare of the people, which is of great concern and is a matter of national interest. Calculation of percentage error helps policymakers assess the probable scope of deviation and formulate their decisions accordingly.

  • The concept of percentage error is also important for the people involved in trading shares and stocks. While investing in any shares and stocks, any investor calculates the percentage errors his investments might have to bear.
  • Before making business decisions, percentage errors are always taken into account. This can be supported using an example. For an outlet in a food court, the number of guests expected on weekdays might go wrong by 25%. 

Still, the number of guests expected on any weekend has less probability of going wrong .since many people prefer to dine outside on weekends, there is less than a 1% chance of the expected number of guests going wrong.

  • Percentage errors are critically important for all the test-based entrance exams. These students writing these exams calculate their scores, keeping in mind their errors while writing answers. In exams with negative marking, the importance of per cent errors is even high.
  • The concept of percentage errors is also vital at the micro-level; even running a household on a budget might involve percentage errors.
  • In the recent situation of the pandemic in our country, the percentage errors were at a peak. While preparing for medical facilities across the length and the breadth of our nation, our health officials made massive errors in expecting the number of covid 19 positive patients. 

The percentage of errors went up as high as 2000%. As a result of these errors, our health system went up for a toss but looking at the errors, our officials are better prepared for the next wave of pandemics.


Percentage errors are easy and scoring questions. Just all you need to do is get the concepts right and understand the basic logic behind them. Lastly, add the final touch by practising enough questions to ensure you have got it in your grasp. 


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