What is the difference between percent error and percentage change?

Percent error compares a measured value to a known accepted value to assess accuracy. Percentage change compares two values over time without implying one is 'correct'.

Why do we use the absolute value in the percent error formula?

Taking the absolute value gives a non-negative percent error representing the magnitude of inaccuracy. The sign of the absolute error separately tells you if you over- or underestimated.

What is a good percent error?

It depends on the field. In many physics experiments, under 5% is acceptable. In chemistry or engineering, tighter tolerances (under 1–2%) may be required.

What is the difference between absolute error and relative error?

Absolute error is the actual numerical difference (Experimental - Theoretical). Relative error is that difference divided by the theoretical value, giving a unitless ratio.

What does a percent error of 0% mean?

A 0% percent error means your measured value exactly matches the accepted value — a perfect measurement, which is rare in practice.

Math

↵ to calculate

Percent Error Calculator — Experimental Error Formula

Calculate percent error between an experimental value and a theoretical or accepted value. Used in science and engineering.

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How to use this calculator

👉 Fill in the boxes below and your answer appears instantly — no maths needed, we do it all for you! 🎉

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In plain English — what does this do?

🍬 Say you have 100 candies. If you eat 20 of them, you ate 20% (20 out of 100). This tool helps you quickly find out ‘what part of a number is something?’ — super easy!

📌 Direct Answer & Summary

Percent error measures how close an experimental or measured value is to a known theoretical or accepted value, expressed as a percentage. It is widely used in chemistry, physics, and engineering labs to evaluate the accuracy of measurements and experiments.

Experimental (measured) value

Theoretical (accepted) value

What is Percent Error Calculator — Experimental Error Formula?

How to use it

1️⃣ Enter your experimental (measured) value in the first field.
2️⃣ Enter the theoretical (accepted or true) value in the second field.
3️⃣ The percent error, absolute error, and relative error all appear instantly.
4️⃣ A positive result means you overestimated; a negative result means you underestimated.

Formula

Percent error = (|Experimental - Theoretical| / |Theoretical|) × 100. Absolute error = Experimental - Theoretical. Relative error = (Experimental - Theoretical) / Theoretical.

💡 See it in action — a real example

If you measured gravity as 9.8 m/s² and the accepted value is 9.81 m/s², the percent error is |9.8 - 9.81| / 9.81 × 100 ≈ 0.102%. The absolute error is -0.01 m/s² (an underestimate).

❓ Common questions

What is the difference between percent error and percentage change?: Percent error compares a measured value to a known accepted value to assess accuracy. Percentage change compares two values over time without implying one is 'correct'.
Why do we use the absolute value in the percent error formula?: Taking the absolute value gives a non-negative percent error representing the magnitude of inaccuracy. The sign of the absolute error separately tells you if you over- or underestimated.
What is a good percent error?: It depends on the field. In many physics experiments, under 5% is acceptable. In chemistry or engineering, tighter tolerances (under 1–2%) may be required.
What is the difference between absolute error and relative error?: Absolute error is the actual numerical difference (Experimental - Theoretical). Relative error is that difference divided by the theoretical value, giving a unitless ratio.
What does a percent error of 0% mean?: A 0% percent error means your measured value exactly matches the accepted value — a perfect measurement, which is rare in practice.

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