About this tool
Three small calculators in one: percent error of an experimental value against a theoretical one, percent difference between two values, and percent change from an old value to a new one. Each updates live in your browser.
Frequently asked questions
What is the difference between percent error and percent change?
Percent error measures how far a measured value is from a known true value, while percent change compares an old and new value and can be positive (increase) or negative (decrease).
How is percent difference calculated?
It is the absolute difference between two values divided by their average, times 100 — useful when neither value is a reference baseline.