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Percent Error Calculator

Percent error between measured and accepted values with steps.

Quick answer

How do you calculate percent error?

Subtract the actual value from the measured value, take the absolute value, divide by the actual value, and multiply by 100. Measuring 9.5 g when the true mass is 10 g: |9.5 − 10| ÷ 10 × 100 = 5% error.

Percent error = |measured − actual| ÷ |actual| × 100

Percent Error Calculator

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Answer
Percent error = 5% (under by 0.5)
  1. Error = measured − actual = 9.5 − 10 = -0.5
  2. Absolute error = |-0.5| = 0.5
  3. Percent error = 0.5 ÷ |10| × 100 = 5%

Compare a measured (experimental) value to the true (accepted) value and get the percent error with steps.

About this Percent Error Calculator

The Percent Error Calculator compares an experimental or measured value with the true, accepted, or theoretical value. It is the standard accuracy check in chemistry, physics, and biology labs, and shows the absolute error and every step.

What you'll need

  • • Measured (experimental) value
  • • Actual (accepted / theoretical) value

How it works

  1. 1. Enter your measured value.
  2. 2. Enter the accepted value.
  3. 3. Read the percent error.
  4. 4. See if you were over or under.
  5. 5. Copy the steps into your lab report.

Worked example

Boiling point measured at 98.2 °C vs 100 °C accepted: |98.2 − 100| ÷ 100 × 100 = 1.8% error.

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Percent Error Calculator FAQ

What is the Percent Error Calculator?

The Percent Error Calculator is a free online tool that helps you percent error between measured and accepted values with steps.

How do I use the Percent Error Calculator?

Open the Percent Error Calculator, enter the requested values, and review the instant estimate on the page.

Is the Percent Error Calculator free?

Yes. The Percent Error Calculator is free to use on Fast Online Calculator and does not require an account.

Can percent error be negative?

Standard percent error uses absolute value, so it is never negative. Some teachers keep the sign to show over (+) or under (−) — the steps show both.

What is a good percent error?

In school labs, under 5% is usually considered good, and under 10% acceptable — check your teacher's rules.

Why can't the actual value be zero?

You'd be dividing by zero. Use absolute error instead.

Percent error vs percent difference?

Percent error compares to a known true value. Percent difference compares two measurements when neither is known to be correct.

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