Percent Error

What Is Percent Error?

Percent error tells you how close your measured (experimental) value is to the actual or accepted (theoretical) value. It’s a way to measure accuracy in science.

• The lower the percent error, the more accurate your result is.

• Theoretical Value = the correct or accepted value (e.g., what the buret delivered on average)

• Experimental Value = your measured value (e.g., what the glassware delivered on average)

• <5% is considered accurate.

Why It Matters in Chemistry

In chemistry labs, you're often trying to measure or produce a certain known amount — like delivering 15.00 mL of liquid. While precision (standard deviation) tells us how consistent your trials were, percent error shows how close you got to the correct value.

This matters when comparing different tools:

• A graduated cylinder might give you close to 15.00 mL.

• A beaker might be way off — even if you poured the same amount each time.