Accuracy Formula
The accuracy formula helps to know the errors in the measurement of values. If the measured value is equal to the actual value then it is said to be highly accurate and with low errors. Accuracy and error rate are inversely related. High accuracy refers to low error rate, and high error rate refers to low accuracy. The accuracy formula gives the accuracy as a percentage value, and the sum of accuracy and error rate is equal to 100 percent.
What is Accuracy Formula?
The accuracy formula provides accuracy as a difference of error rate from 100%. To find accuracy we first need to calculate the error rate. And the error rate is the percentage value of the difference of the observed and the actual value, divided by the actual value.
Accuracy = 100%  Error Rate
Error Rate = Observed Value  Actual Value/Actual Value × 100
Let us look at a few examples below, to understand more about the accuracy formula.
Solved Examples on Accuracy Formula

Example 1: The length of a rectangular box is 1.2 meters, but it was measured with tape, and the length was measured as 1.22 meters. Find the accuracy of measurement.
Solution:
Given the length of the rectangular box = 1.20 meters
The measured length of the rectangular box = 1.22 meters
\(\begin{align} \text{Error Rate} &= \dfrac{\text{Measured Value  Given Value}}{\text{Given Value}} \times 100 \\&=\frac{(1.22  1.20)}{1.20} \times 100 \\& = \frac{0.02}{1.20} \times 100 \\&= 1.67\% \end{align} \)
Accuracy = 100%  Error% = 100%  1.67% = 98.33%
Answer: Hence the accuracy is 98.33% 
Example 2: A measuring tape can measure with an accuracy of 99.8%. What is the possible range of length which can be obtained by using this measuring tape, to measure a cloth of length 2 meters?
Solution:
The given accuracy of the measuring tape = 99.8%
The error rate for the measurement = 100%  99.8% = 0.2%
The length of the cloth = 2 meters
The new measurement using this measuring tape = \( 2 m \pm 0.2\% \times2m = 2 \pm 0.004\)
Maximum value of the measurement would be 2m + 0.004 = 2.004m
Minimum value of the measurement would be 2m  0.004m = 1.996m
Answer: Hence the range of measures that can be obtained is from 1.996m to 2.004m.
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