Free Electrical Tools
Professional electrical calculation tools for NEC compliance. All tools are free, accurate, and designed for electricians.
Box Fill CalculatorMost Popular
Calculate electrical box fill per NEC 314.16 with a clear, itemized volume breakdown.
Wire Gauge Chart
Complete AWG wire gauge chart with conductor volume allowances per NEC Table 314.16(B).
NEC Code Reference
Quick reference guide for NEC 314.16 electrical box fill requirements and code sections.
Volume Converter
Convert between cubic inches and cubic centimeters for electrical box volume calculations.
Conduit Fill Calculator
Calculate conduit fill percentage per NEC Chapter 9. Supports EMT, IMC, and RMC conduit.
Pull Box Sizing vs Box Fill Guide
Separate NEC 314.16 box-fill volume from NEC 314.28 pull-box length, angle-pull, and U-pull sizing rules.
Voltage Drop and Box Fill Guide
Plan long branch circuits without missing NEC 314.16 box volume, conductor upsizing, device yokes, clamps, and grounding allowances.
Conductor Derating and Box Fill Guide
Separate NEC 310.15 ampacity derating from NEC 314.16 box-fill volume when conductor size or count changes.
Surge Protective Device Box Fill Guide
Size SPD junction boxes with NEC 314.16, NEC 242, grounding, conductor length, internal clamps, and IEC surge-protection context.
USB-C Receptacle Box Fill Guide
Size USB-C, USB-A, and combination receptacle boxes with NEC 314.16 device-yoke, grounding, clamp, and conductor-count examples.
EV Charger Box Fill Guide
Worked box-fill examples for NEMA 14-50 outlets, hardwired EVSE wallboxes, 40 A and 60 A charging circuits, and outdoor charger junctions.
Wire Connector Box Fill Guide
NEC 314.16 examples for wire nuts, lever connectors, splice bundles, pigtails, and practical box volume.
Box Fill Chart
Quick chart for common electrical box sizes, conductor-only capacity, and practical box choices before you run the exact NEC calculation.
Box Fill Calculator PDF
Download a printable NEC 314.16 worksheet PDF for field counts, rough-in notes, and final box-volume checks.
Ceiling Fan Box Fill Guide
Worked examples for fan-rated ceiling boxes, support fittings, and conductor counts under NEC 314.16 and NEC 314.27.
Aluminum Wire Box Fill Guide
Worked box-fill examples for aluminum branch circuits, receptacle repairs, feeder splices, and NEC 110.14 / 314.16 checks.
Mini-Split Disconnect Guide
Box fill and enclosure sizing advice for mini-split disconnect-adjacent boxes, whip transitions, and upsized HVAC conductors.
Generator Inlet Guide
Box fill and enclosure sizing advice for portable generator inlet boxes, transfer-adjacent splices, and larger backup-power conductors.
Water Heater Guide
Box fill and enclosure sizing advice for storage water heaters, tankless circuits, disconnect-adjacent boxes, and larger branch-circuit conductors.
Essential Electrical Calculation Tools
Our suite of free electrical tools helps electricians, contractors, and engineers perform accurate calculations for NEC compliance.
Why Use Our Electrical Tools?
- NEC NEC Compliant: All calculations follow current National Electrical Code requirements
- Always Free: No registration, no subscriptions, no hidden fees
- Mobile Friendly: Use on any device, perfect for on-site calculations
- Regularly Updated: Updated for NEC 2023 including terminal block requirements