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Percent Error Calculator

Last updated: June 2026

Percent error

Percent error measures how close an experimental or estimated value is to an accepted true value.

Percent error

5%

Absolute error

0.5

Relative error

0.05

Accuracy interpretation

Good - acceptable for most experiments.

What counts as a good percent error?

< 5%
Excellent

5-10%
Good

10-20%
Fair

> 20%
Poor

Step-by-step working
  1. Step 1: |9.5 - 10| = 0.5.
  2. Step 2: 0.5 / |10| = 0.05.
  3. Step 3: multiply by 100 = 5%.
  4. Result: 5% error.

What is percent error?

Percent error compares an experimental measurement with an accepted value. It is often used in science labs to judge how accurate a result was.

Percent error vs percent difference

Percent error needs a known true value. Percent difference is used when comparing two measured values where neither one is treated as the correct answer.

How to reduce experimental error

Repeat measurements, calibrate equipment, control variables, use appropriate significant figures, and check for systematic bias in the method.

About this calculator

The Percent Error Calculator compares a measured value with an accepted or actual value. It is commonly used in science experiments, lab reports, quality checks, and measurement accuracy work.

percent error calculator formula

Percent error divides absolute error by the accepted value, then multiplies by 100. Some contexts also use signed error to show whether the measurement was high or low.

  • absolute error = |measured - actual|
  • percent error = |measured - actual| / |actual| x 100
  • signed error = (measured - actual) / actual x 100

How to use the percent error calculator

  1. Enter the measured or experimental value.
  2. Enter the actual or accepted value.
  3. Find the absolute difference.
  4. Divide by the absolute actual value.
  5. Multiply by 100.
  6. Use the interpretation only as a general guide.

Worked examples

Science experiment

Input: Measured 9.5, actual 10

Calculation: |9.5 - 10| / 10 x 100

Result: 5% error

High estimate

Input: Measured 108, actual 100

Calculation: |108 - 100| / 100 x 100

Result: 8% error

Systematic vs random error

Systematic error pushes results consistently in one direction. Random error varies between measurements. Percent error does not identify the cause, but it can show the size of the difference.

Percent error in school science

Percent error is often used to discuss experimental accuracy, but the acceptable level depends on the experiment, equipment, and marking scheme.

Percentage calculation note

This calculator is for education, checking, and general planning. Percentage results depend on the inputs and the chosen method, so check whether your question asks for percent change, percent difference, percent error, reverse percentage, or a simple conversion.

  • Percent change has direction, but percent difference does not.
  • Reverse percentage calculations can be confused with percentage increase or decrease.
  • Rounded percentages may not reverse exactly to the original values.

Frequently asked questions

Does this show the working?

Yes. The percentage calculators show the key formula and calculation steps.

What does percent mean?

Percent means per hundred, so 25% means 25 out of 100.

Why do some percentage answers differ?

Different percentage questions use different reference values. Percent change, percent difference, and percent error are not the same.

Can percentages be more than 100?

Yes. A percentage can be above 100 when a value is larger than the reference whole.

Should I round the answer?

Round only to the precision required by your homework, report, invoice, or calculation context.

Related calculators

  • Percent Difference Calculator
  • Percent Change Calculator
  • Marks Percentage Calculator

What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.

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