🔌 Free Calculator — 30 Seconds to the Right Cord

What Gauge Extension Cord
Do You Actually Need?

Pick the appliance, tell it how long the cord run is, and get the answer — the same numbers as the chart, without reading a table. Remember: with gauge, a lower number means a thicker, stronger cord.

⚠️ Two rules the calculator will not bend: space heaters plug into a wall outlet ONLY — every manufacturer says so, and this tool will never recommend a cord for one. And generators plug into appliances, NEVER into a wall outlet — backfeeding can kill the utility lineman fixing your street.

Where these numbers come from: the recommendations match the gauge chart on the Extension Cord Guide, built on published National Electrical Code ampacity guidance and safety-council (ESFI/UL) recommendations, rounded to the heavier gauge wherever a draw sits near a boundary. Longer runs need thicker cords because voltage drops over distance — a starved motor runs hot and dies young. Your appliance’s label and manufacturer instructions are always the final word. Running several things on one cord? Add their amps together and use the total. Outdoors, the cord jacket must be marked “W”. General educational information only — see the full disclaimer.

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Calculator Disclaimer: This tool provides general estimates for informational and planning purposes only. Actual generator sizing should be verified by a licensed electrician or generator installer who can inspect your home's electrical panel and specific appliance loads. Propane consumption figures are estimates based on typical generator efficiency at partial load — actual usage will vary. Cost estimates reflect general regional market conditions and are not quotes. Always consult a licensed propane installer and electrical contractor before purchasing or installing any generator system. © 2026 Franklyns Bay LLC. In any emergency, follow official guidance from FEMA Ready.gov and your local emergency management authority. Franklyns Bay LLC assumes no liability for decisions made based on this tool. Full disclaimer →