Free Physics tool · Step by step

Percent Error Calculator

Calculate percent error from your experimental (measured) value and the accepted (theoretical) value, with the formula and steps for your lab report. Free for physics and chemistry labs.

Percent error

1.937%

Signed: -1.937% (measured low)

  1. 1

    Formula

    %  exterror=\ rac∣ extexperimental− extaccepted∣∣ extaccepted∣ imes100\%\,\ ext{error} = \ rac{|\ ext{experimental} - \ ext{accepted}|}{|\ ext{accepted}|}\ imes 100
  2. 2

    Find the difference

    9.62−9.81=−0.199.62 - 9.81 = -0.19
  3. 3

    Divide by the accepted value and multiply by 100

    ∣−0.19∣∣9.81∣×100=1.937%\frac{|-0.19|}{|9.81|}\times 100 = 1.937\%
  4. 4

    Direction: your value is too low

    Signed error = -1.937%. Lab reports usually quote the absolute value.

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FAQ

What is the percent error formula?

Percent error = |experimental − accepted| ÷ |accepted| × 100.

Can percent error be negative?

The signed error is negative when your measured value is below the accepted value. Lab reports usually quote the absolute value, which is never negative.

Is percent error the same as percent difference?

No — percent difference compares two measured values using their average; percent error compares a measurement with a known accepted value.

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