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Frequently asked about the Percent Error
What does the Percent Error do?
The Percent Error solves the common mathematics and arithmetic question: expected vs actual. Enter your numbers on the left, the answer updates instantly on the right — no submit button, no signup.
Is the Percent Error free to use?
Yes. Every calculator on CalcMaster is free, has no usage caps, requires no signup, and shows no ads. The site is open-source-friendly and supported entirely by the author.
Does the Percent Error work on mobile?
Yes. CalcMaster is fully responsive and installable as a PWA — on Android tap the browser menu → "Add to Home Screen"; on iOS Safari → Share → "Add to Home Screen". After installing, the Percent Error works offline.
Where is my input stored?
Nowhere by default. Your inputs live in your browser's memory while you're on the page; a copy of your recent calculations is saved to localStorage on your device so the History page works. Nothing is sent to a server unless you explicitly enable cloud sync.
Can I trust the formula in the Percent Error?
The math is sourced from peer-reviewed and standard public formulas; you can read the formula in the result card. For decisions involving real money or health, always cross-verify with a qualified professional — calculators are educational, not advice.