Updated on September 8th, 2025

Percent Error Calculator

Created By Jehan Wadia

⚛️ Physics
Gravity measurement
🧪 Chemistry
Concentration analysis
⚙️ Engineering
Material strength
📊 Statistics
Population estimate
% Error = |Experimental - Theoretical| / |Theoretical| × 100

Introduction

The Percent Error Calculator helps you find how far off your guess or measurement is from the true value. When you measure something or make a prediction, it might not be exactly right. Percent error tells you the size of your mistake as a percentage. This makes it easy to see if your answer was close or far from the correct one.

Scientists, students, and workers use percent error all the time. In science class, you might measure the length of a table and compare it to the real length. In a store, someone might guess how many items will sell and later check their guess. The percent error shows them how good their guess was. A small percent error means you were close to being right. A big percent error means you were far off.

How to use our Percent Error Calculator

Enter your measured value and true value to find out how far off your measurement was from the expected result. The calculator will show you the percent error as a percentage.

Calculation Mode: Pick what you want to find - percent error (most common), experimental value, or theoretical value.

Experimental/Observed Value: Type in the number you got from your experiment or measurement. This is what you actually measured.

Theoretical/True Value: Type in the correct or expected value. This is what the answer should have been.

Error Type: Choose if you want the error to always be positive (absolute) or if it can be negative (signed) to show if you measured too high or too low.

Decimal Places: Pick how many numbers you want after the decimal point in your answer.

Acceptable Error Threshold: Set a maximum percent error that would be okay for your work. This is optional and helps you know if your error is too big.

Understanding Percent Error in Statistics

Percent error is a way to measure how far off your measured value is from the true value. When you do an experiment or take a measurement, your result might not match the expected answer perfectly. Percent error tells you how big that difference is as a percentage.

How Percent Error Works

To find percent error, you compare two values: the experimental value (what you measured) and the theoretical value (what should be correct). The formula takes the difference between these numbers, divides by the theoretical value, and multiplies by 100 to get a percentage. A smaller percent error means your measurement was more accurate.

When to Use Percent Error

Scientists use percent error all the time. In physics class, you might measure gravity and compare it to the known value. In chemistry, you might test the concentration of a solution. Engineers check if materials are as strong as they should be. Any time you need to know how close your measurement is to the correct answer, percent error helps. When tracking performance in gaming, you might use a KD Calculator or KDA Calculator to measure accuracy in a different way.

What Makes a Good Percent Error

A percent error under 1% is excellent and means your measurement is very accurate. Between 1% and 5% is still good for most experiments. From 5% to 10% is acceptable for many situations, especially in school labs. Over 10% usually means something went wrong or your measuring tools aren't precise enough. Remember that some experiments are harder than others, so what counts as "good" can change based on what you're measuring.

Important Things to Remember

Percent error can be positive or negative. A positive error means you measured too high, while negative means too low. Most times, people use absolute percent error, which is always positive because they only care about how far off they were, not which direction. Also, you can't calculate percent error if the theoretical value is zero, because you can't divide by zero. In physics experiments, you might also need other calculators like the Free Fall Calculator or Kinetic Energy Calculator to verify your theoretical values before calculating percent error.


Frequently Asked Questions

What is the difference between experimental value and theoretical value?

The experimental value is what you actually measure or observe in your test. It's the number you get when you do the experiment yourself. The theoretical value is what the answer should be based on facts or formulas. It's the correct or expected value that you compare your measurement to.

Can percent error be negative?

Yes, percent error can be negative when you use signed error. A negative percent error means your measured value was lower than the true value. If you use absolute error (which is more common), the percent error is always positive because it only shows how far off you were, not which direction.

Why can't I calculate percent error when the theoretical value is zero?

You can't calculate percent error with a theoretical value of zero because the formula divides by the theoretical value. Dividing by zero is not possible in math. When the true value is zero, you need to use a different way to measure error, like absolute error instead of percent error.

What is batch mode in the calculator?

Batch mode lets you calculate percent error for many pairs of values at once. Instead of doing one calculation at a time, you can enter multiple experimental and theoretical values separated by commas. The calculator will find the percent error for each pair and give you statistics like the average error for all your measurements.

How do I know if my percent error is acceptable?

It depends on what you're measuring. For most school experiments, under 10% is acceptable. In professional work, under 5% is often needed. Very precise work might need under 1%. You can set an error threshold in the calculator to check if your error is within acceptable limits for your specific needs.

What does the error gauge show?

The error gauge is a colored bar that shows how big your percent error is. Green means low error (good), yellow means medium error (okay), and red means high error (poor). The pointer shows where your specific error falls on this scale, making it easy to see at a glance how accurate your measurement was.