Ever compared a measurement to an expected value and wondered “How far off was I?” That’s where percent deviation comes in! It’s a quick and simple way to show how close or far a result is from what you expected — and it’s super useful in science, business, and everyday life.
Let’s explore how it works and how to calculate it easily using our online tool!
Table of Contents
🙋 What Is Percent Deviation?
Percent deviation tells you how much a measured value differs from the expected (or theoretical) value, expressed as a percentage.
It answers the question:
“By what percent did the actual result deviate from the expected result?”
It’s especially useful when you want to evaluate the accuracy of a measurement or test.
🔢 Percent Deviation Formula
Here’s the formula:
Percent Deviation = (|Measured − Expected| / Expected) × 100
Where:
- Measured is the observed or experimental value
- Expected is the standard, theoretical, or target value
- The absolute value ensures you always get a positive result
🧮 Percent Deviation Example
Let’s say:
- Measured value = 95
- Expected value = 100
Percent Deviation = (|95 − 100| / 100) × 100 = (5 / 100) × 100 = 5%
So, your result deviated by 5% from the expected value.
📊 When to Use It
Percent deviation is widely used in:
- Science labs to check experiment accuracy
- Quality control in manufacturing
- Finance and data analysis for error tracking
- Education to assess grading consistency or scoring differences
✨ Why Use a Calculator?
Sure, you can do the math manually — but a percent deviation calculator helps you:
- Avoid errors
- Save time with repeated calculations
- Easily compare multiple values