Percent Error Calculator

Math Tools

How far an experimental value is from the true value

FreePrivateInstant
Measured (experimental) value
Accepted (true) value
Full guide, 3 min readPercent error: how far off is your measurement, and how it differs from percent changeRead the story behind this tool →
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History

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Percent Error Calculator — at a glance

Check how accurate a measurement is.

You enter
Measured 9.6
True 9.81
Calculate Error
Result
Percent error

How to use it — step by step

The measured value and the accepted (true) value.

1

Enter your values

Fill in the fields. Default numbers are shown so you can see how it works.

2

Press Calculate Error

The answer appears at once as large result cards.

3

Copy or share

Copy the result, or share a link that opens with your numbers filled in.

Pro tips

Small things that make the result better.

✦Percent error = |measured − true| ÷ |true| × 100.
✦The true value cannot be zero.
✦A lower percent means a more accurate result.

Quick facts

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Frequently Asked Questions

Can percent error be negative?+

The usual formula uses the absolute value, so it is positive. The sign of the error is shown separately.

What is a good percent error?+

Under 5% is fine for many school experiments.

Is my data safe?+

Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.

Is this tool really free?+

Yes — completely free, no signup, no watermark and no usage limit.

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Percentage Change CalculatorUp 50 percent, down 50 percent, and you are not back to zero