“Free Percent Error Calculator – quickly compare observed and expected values with step-by-step results.”
Percent Error Calculator
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📏 How to Use the Percent Error Calculator (Free & Pro)
The Percent Error Calculator helps you measure how accurate an experimental or observed value is compared to a theoretical or true value. It’s widely used in science, chemistry, physics, and engineering to calculate the difference between measured and expected results as a percentage.
This tool instantly gives you the percent error, showing how close your result is to perfection — whether you’re in a classroom lab or analyzing data.
- Enter the experimental (measured) value: Type the value you obtained in your experiment.
- Enter the theoretical (true) value: Add the value you expected or calculated theoretically.
- Click Calculate: The calculator instantly displays your percent error and absolute difference.
- Reset: Use this button to clear both fields and start a new calculation.
💡 Example: If the theoretical value is 100 and your measured value is 92, the percent error = 8%.
Formula:
Percent Error = |(Experimental − Theoretical)| ÷ |Theoretical| × 100%
Where:
- Experimental value = the value you measured
- Theoretical value = the correct or accepted value
- | | = absolute value (ignore negative signs)
⚡ A smaller percent error means higher accuracy. A larger one indicates possible errors in measurement or calculation.
- 📊 Compare multiple experiments side by side
- 📥 Export results to PDF or Excel
- 📈 Visual charts for error trends across trials
- 🧠 Advanced settings for relative and absolute error analysis
💎 Upgrade to Percent Error Calculator Pro for all advanced features.
- Measured = 47, True = 50 → Percent Error = 6%
- Measured = 99, True = 100 → Percent Error = 1%
- Measured = 85, True = 100 → Percent Error = 15%
✅ 0–5%: Excellent accuracy
⚠️ 5–10%: Acceptable in most lab conditions
❌ 10%+: Indicates significant error or inaccuracy
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Open ToolPercent Error Calculator – Calculate Percentage Error & Accuracy Online
Use our free Percent Error Calculator to find how accurate your measurements or predictions are compared to the true or accepted value. Perfect for students, teachers, scientists, and engineers, this tool helps you determine how far your result deviates from the expected value in percentage form.
What Is Percent Error?
Percent error measures the difference between an experimental (measured) value and the accepted (true) value, expressed as a percentage. It shows the accuracy or reliability of your measurement or calculation.
Percent Error Formula
Formula:
Percent Error = |(Measured Value − True Value)| ÷ |True Value| × 100
Where:
- Measured Value = your experimental or observed value
- True Value = the known or accepted value
- The vertical bars | | mean absolute value (ignore negative signs)
How to Use the Percent Error Calculator
- Enter the measured (observed) value.
- Enter the true (accepted) value.
- Click “Calculate” to see the percent error instantly.
- Use results to understand how accurate your measurement or experiment was.
Percent Error Example
Example: Suppose the measured density of a material is 8.2 g/cm³, and the true density is 8.0 g/cm³.
| Step | Calculation | Result |
|---|---|---|
| 1. Difference | |8.2 − 8.0| | 0.2 |
| 2. Divide by True Value | 0.2 ÷ 8.0 | 0.025 |
| 3. Multiply by 100 | 0.025 × 100 | 2.5% |
Percent Error = 2.5%
How to Interpret Percent Error
- Low Percent Error: High accuracy (measured value close to true value).
- High Percent Error: Low accuracy (large difference from true value).
Common Uses of Percent Error
- Science Experiments: Measure accuracy of results vs accepted values.
- Physics & Chemistry: Compare experimental results to theoretical ones.
- Engineering: Check precision in measurements or quality control.
- Finance & Data: Analyze prediction accuracy in models or forecasts.
Difference Between Percent Error & Percent Difference
- Percent Error: Compares a measured value to a known true value.
- Percent Difference: Compares two measured values without a true standard.
Frequently Asked Questions (FAQ)
1. Can percent error be negative?
No — the formula uses absolute value (| |), so the result is always positive.
2. What is a good percent error?
It depends on context — less than 5% is excellent for most experiments, 10% is acceptable, and above 20% indicates large deviation.
3. What causes a high percent error?
Errors can result from poor measurement tools, calculation mistakes, or environmental factors affecting accuracy.
4. Can this calculator handle negative or decimal inputs?
Yes! It works with any numeric value, including negatives and decimals.
Final Thoughts
The Percent Error Calculator is a quick and reliable way to evaluate accuracy in experiments, tests, and predictions. Use it to understand deviations between actual and expected results — and improve precision in your calculations.
Useful Links:
Standard Deviation Calculator |
Percentage Calculators |
Scientific Calculator |
Exponent Calculator |
WHO – Data & Statistics Info