Calculate Percentage Error

Calculating percentage error allows you to compare an estimate to an exact value. The percentage error gives you the difference between the approximate and exact values as a percentage of the exact value and can help you see how close your guess or estimate was to a real value. If you want to know how to calculate percentage error, all you need to know is the approximate and exact value and you'll be on your way.

Steps

1. Know the formula for calculating percentage error. The formula for calculating percentage error is simple:'[(|Exact Value-Approximate Value|)/Exact Value] x 100
   • The approximate value is the estimated value, and the exact value is the real value. Once you find the absolute value of the difference between the approximate value and exact value, all you need to do is to divide it by the exact value and multiply the result by 100.
2. Subtract the real number from your number. This means that you should subtract the real value from the estimated value. In this case, the real value is 10 and the estimated value is 9.
   • Ex: 10 - 9 = 1
3. Divide the result by the real number. Simply divide -1, the result when 10 is subtracted from 9, by 10, the real value. Place the fraction in decimal form.
   • Ex:-1/10 = -0.1
4. Find the Absolute Value of a Number The absolute value of a number is the value of the positive value of the number, whether it's positive or negative. The absolute value of a positive number is the number itself and the absolute value of a negative number is simply the value of the number without the negative sign, so the negative number becomes positive.
   • Ex: |-0.1| = 0.1
5. Multiply the result by 100. Simply multiply the result, 0.1, by 100. This will convert the answer into percent form. Just add the percentage symbol to the answer and you're done.
   • Ex: 0.1 x 100 = 10%

Tips

• Some teachers like the percent error to be rounded to a certain point; most people will be satisfied with the percent error rounded to three significant digits.

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Sources and Citations

See also

• Modify a Brief Linear Regression Model in Excel
• Make a Pie Chart
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• Calculate Range
• Find the Mode of a Set of Numbers
• Calculate Odds
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• Make a Box and Whisker Plot
• Calculate P Value
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