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Accuracy Calculator


Table of Content


Accuracy calculator helps you determine how accurate a measured value or experiment result is by comparing it to the actual or expected value. It helps in evaluating the level of correctness and precision of the data using three different methods.

The first two methods are commonly used to assess diagnostic tests, while the third method can be applied across various fields of science.

How to Calculate Accuracy?

The recommended way to calculate the accuracy using an accuracy calculator. But if you want to calculate it manually, follow the methods accordingly:

1. Standard Accuracy for Diagnostic Tests:

Standard accuracy, also known as global accuracy, is a measure of the overall accuracy of a diagnostic test. It is calculated by dividing the number of correct diagnoses by the total number of diagnoses, such as:

Standard Accuracy = (True Positives + True Negatives) / (True Positives + True Negatives + False Positives + False Negatives)


  • True positives – The number of cases that were correctly identified as positive
  • True negatives – The number of cases that were correctly identified as negative
  • False positives – The number of cases that were incorrectly identified as positive
  • False negatives – The number of cases that were incorrectly identified as negative

2. Accuracy Based on Prevalence:

To calculate accuracy based on prevalence use the following accuracy formula:

Accuracy = ((Sensitivity) × (Prevalence)) + ((Specificity) × (1 – Prevalence))

You'll need to follow these steps:

1. Identify the sensitivity and specificity of the diagnostic test. A sensitivity test is used to determine the proportion of positive cases that are accurately identified as positive, while specificity is the proportion of negative cases that are correctly identified as negative.

2. Determine the prevalence of the disease within the population to be tested. Prevalence is the proportion of the population that has the disease.

3. Replace the values for sensitivity, specificity, and prevalence in the accuracy equation:

Accuracy = ((Sensitivity) × (Prevalence)) + ((Specificity) × (1 – Prevalence))

4. Evaluate the expression to get the accuracy based on prevalence.

3. Percentage Accuracy:

Here are some steps shown below which you can follow to find the percentage accuracy:

Step 1: Calculate the absolute value of the difference between the observed value (Vo) and the actual value (Va).

An absolute value is defined as the distance from zero of a number. In this case, the absolute value of the difference between Vo and Va represents the magnitude of the error.

Step 2: Divide the absolute value of the difference by the actual value (Va).

This step normalizes the error by expressing it as a proportion of the actual value. This allows for the comparison of errors across different measurements or populations.

Step 3: Multiply the result by 100 to express it as the percentage error.

This step converts the error from a decimal form to a percentage, making it easier to interpret and compare.

Here's the formula for calculating percent accuracy:

Percent accuracy error = (|(Vo – Va)|/Va) × 100


  • Vo is the observed value
  • Va is the value accepted as truth
  • |(Vo - Va)| is the absolute, non-negative value

Accuracy vs. Precision:

Have a look at this chart to get a clear idea about accuracy and precision:

Feature Accuracy Precision
Definition How close a measurement is to the true or actual value. How close multiple measurements of the same thing are to each other.
Focus Hitting the bullseye of a target. Grouping arrows tightly together.
Importance Ensuring reliable and valid results. Enabling consistent and repeatable results.
Application Scientific measurements, data analysis, and quality control. Scientific experiments, manufacturing processes, instrument calibration.
Relationship A measurement can be both accurate and precise, or one without the other. High precision often contributes to accuracy, but accuracy does not guarantee precision.


What is Accuracy?

“Accuracy means how close a measurement or results is to the real or expected value.”

It's about getting the measurement as close as possible to the true value without making mistakes.

Can Accuracy Be 100%?

yes, accuracy can be 100%. This means that a measurement or result is perfectly correct and matches the true or expected value exactly. However, achieving 100% accuracy can be very challenging in many real-world situations due to various factors such as limitations in measurement tools, human error, or the complexity of the process being measured.

How can I Improve the Accuracy of My Measurements?

Here are some simple tips for improving the accuracy of your measurements:

  • Use calibrated instrument: Calibration ensures that your instruments are measuring what they are supposed to measure and that they are doing so consistently.
  • Take multiple measurements: The more measurements you take, the more confident you can be in your results.
  • Use a consistent technique: Make sure you are using the same technique each time you take a measurement to minimize variability.
  • Eliminate distractions: Distractions can affect your focus and lead to errors in your measurements.
  • Double-check your work: Always double-check your measurements and accuracy calculations to make sure they are correct.

References: Accuracy and precision, Common technical definition, In classification

Shaun Murphy

I'm graduated in biomedical and electrical engineering. Specialization in sports and medical topics but will gladly tackle everything you throw at him. He is a sailor, hiker, and motorcyclist in his free time.

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