Error Propagation Calculator

Estimate uncertainty in a calculated result for sums, differences, products, quotients, and powers using standard propagation rules.

Engineering MathUncertaintyMeasurement

Calculate

Operation
Power n
x
Uncertainty Δx
y
Uncertainty Δy
Please enter valid values.

What this calculator teaches

Error propagation estimates how measurement uncertainty affects a calculated quantity. It is essential in labs, engineering, physics, and data analysis.

This calculator assumes independent uncertainties and uses common first-order propagation rules.

Formula & Symbols

ConceptFormulaMeaning
Sum/differenceΔz = √(Δx² + Δy²)Absolute uncertainties combine in quadrature.
Product/quotientΔz/|z| = √((Δx/x)² + (Δy/y)²)Relative uncertainties combine in quadrature.
PowerΔz/|z| = |n| Δx/|x|Power rule for z=x^n.

Step-by-Step Examples

Example 1
Adding measurements
  • x = 12 ± 0.2 and y = 5 ± 0.1.
  • z = 17.
  • Δz = √(0.2² + 0.1²).
✓ z = 17 ± 0.224.
Example 2
Multiplying measurements
  • For z = xy, first compute relative uncertainty.
  • Combine relative uncertainties in quadrature.
  • Multiply by |z| to get absolute uncertainty.
✓ Report z ± Δz.

Where students use this

🎓
High school and college
Use the tool to check homework and understand each step.
📊
Data and modeling
Connect formulas to tables, graphs, and real values.
🧪
Science and engineering
Use math results inside physics, chemistry, and engineering problems.
💻
Computer science
Apply the same logic to algorithms, systems, and numerical work.

Common Mistakes to Avoid

⚠️
Adding uncertainties directly

For independent random uncertainties, combine in quadrature, not by simple addition.

⚠️
Using relative uncertainty for sums

Sums and differences use absolute uncertainty.

⚠️
Using absolute uncertainty for products

Products and quotients use relative uncertainty first.

Frequently Asked Questions

What does uncertainty mean?
It describes a reasonable spread around a measured or calculated value.
What does independent uncertainty mean?
It means one measurement error does not depend on the other.
Is this exact?
It is a standard approximation based on small uncertainties.
How should I report the result?
Usually report z ± Δz with sensible significant figures.

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Formula Explorer connections

Interpretation: This method approximates a mathematical solution through iteration, discretization, interpolation or numerical quadrature. Assumption: Accuracy depends on step size, initial guesses, smoothness, conditioning and stopping criteria. Compare error and convergence rather than trusting a single approximation.

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