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Every calculation runs in your browser. WireAndWidgets has no accounts, no database, and no upload. Files you open stay on your machine.
Where your work is saved
Tools that keep your work save it in this browser only. Clearing your browsing data erases it, so use each tool's Export button for a backup file and Import to restore it on any computer. Installing the app makes browsers far less likely to clear it.
About the results
Results are estimates based on common industry ampacity and sizing tables. Always confirm them against the code edition adopted in your area and with your local inspector before you install anything. WireAndWidgets is not affiliated with any code body or manufacturer.