Online Percent Calculator Logo

Percent Error Calculator

Compare your observed (approximate) value with the true (exact) value to find the margin of error.

Measure the accuracy of your estimate or experiment.

Quick Answer

Percent error measures the difference between an estimated value and the actual exact value. The formula is **Percentage Error = |(Approximate - Exact) / Exact| × 100**. It is always a positive number.

Percent Error Calculator

Related Percentage Basics Calculators

Decimal to Percentage Calculator

Enter a decimal value to instantly convert it to its percentage equivalent,...

CALCULATE

Fraction to Percentage Calculator

Easily convert any fraction into a percentage. Enter the numerator (top number)...

CALCULATE

Percentage Change Calculator

Enter the original and new values to see the percentage change. Works...

CALCULATE

Percentage Decrease Calculator

See how much a value has dropped as a percentage. Perfect for...

CALCULATE

Percentage Difference Calculator

Find how much two values differ in percentage terms. Ideal for comparing...

CALCULATE

Percentage Increase Calculator

Measure how much a value has grown as a percentage. Ideal for...

CALCULATE

How It Works

  1. Subtract the Exact Value from the Approximate Value.
  2. Take the absolute value of the result (make it positive).
  3. Divide by the absolute value of the Exact Value.
  4. Multiply by 100.

Formula:

% Error = |(Approx - Exact) / Exact| × 100

Common Uses

- **Chemistry/Physics Labs**: Comparing experimental results to constants. - **Manufacturing**: Checking part tolerance. - **Finance**: Comparing forecast vs actual revenue.

Examples

Example A: Physics Lab

Result: Measured gravity: 9.7 m/s². True gravity: 9.8 m/s². Error: |9.7-9.8|/9.8 = 0.1/9.8 = 1.02%.

Example B: Estimation

Result: Guessed 50 jellybeans. Actual 55. Error: |50-55|/55 = 5/55 = 9.09%.

Frequently Asked Questions

Why is percent error always positive?

Because use absolute value in the numerator. We care about the "magnitude" of the error, not the direction (whether it was too high or too low).

What is a good percent error?

In science labs, under 5% is often considered accurate (good). Under 1% is excellent. It depends on the precision of your instruments.

Is percent error the same as percent difference?

No. Percent error compares a guess to a TRUE value. Percent difference compares two experimental values where neither is "correct".

Related Articles