Calculators & Tools
Free electrical calculators: wire size, voltage drop, "can my panel handle it?" and generator sizing, plus a Federal Pacific / Zinsco panel checker.
Free calculators to help you plan a project and ask good questions. They give general estimates only, so please have a licensed electrician confirm anything before work starts. The problem-panel checker can help you spot panel brands worth a closer look.
Free calculators and tools 5
Wire size calculator
Free wire size calculator: enter amps, copper or aluminum, and distance to see the minimum AWG by NEC 310.16 ampacity and for 3% voltage drop. Rough guide.
Open tool ToolVoltage drop calculator
Free voltage drop calculator: enter wire size, copper or aluminum, amps and one-way distance to see volts lost and percent drop. NEC Chapter 9 Table 8 values.
Open tool ToolCan my panel handle it? (EV, heat pump, hot tub)
Quick, rough check of whether a 100 to 200 amp panel can handle a new EV charger, heat pump or hot tub, using a simplified NEC 220.82 load calculation.
Open tool ToolGenerator sizing estimate
Pick what you want to run in an outage and see running and starting watts, a suggested portable generator size and whether a 30 A or 50 A inlet fits.
Open tool ToolProblem panel and recall checker
Check whether your electrical panel brand has a recall or a known problem history: Federal Pacific Stab-Lok, Zinsco, Challenger, Pushmatic, fuse boxes and more.
Open toolMore sections
- Panels & Service Upgrades
- EV Chargers
- Generators & Battery Backup
- Solar
- Safety & Hazards
- Older Homes & Old Wiring
- Troubleshooting
- Wiring Basics
- Permits & Inspections
- Lighting & Outlets
General information for California homes. Local rules and inspectors can vary. Not a substitute for an on-site inspection.