Grounding NEC 250 Calculator

NEC grounding size calculator for electricians, apprentices, and electrical engineers. Three calculators in one app: Equipment Grounding Conductor (EGC) from Table 250.122, Grounding Electrode Conductor (GEC) from Table 250.66 with sole-connection exceptions, and Bonding Jumper from Table 250.102(C)(1) with the 12.5% rule. This electrical grounding calculator works 100% offline on the job site. Whether you're sizing an EGC for a 200A circuit, determining the GEC for a 500 kcmil service with a ground rod electrode, or calculating a bonding jumper for parallel service conductors, this grounding calculator gives you accurate NEC-compliant results in seconds - perfect for grounding system design and installation verification. THREE CALCULATORS IN ONE: EQUIPMENT GROUNDING CONDUCTOR (EGC): • Size EGC per NEC Table 250.122 - all 21 table rows from 15A to 6000A • All 37 standard OCPD ratings per NEC 240.6(A) selectable - including 30A, 40A, 50A, 70A, 125A • Copper and aluminum conductor support • Voltage drop adjustment per NEC 250.122(B) - proportionally increase EGC when circuit conductors are upsized • Original and adjusted wire size selection for accurate proportional calculation • Automatic rounding up to next standard OCPD rating GROUNDING ELECTRODE CONDUCTOR (GEC): • Size GEC per NEC Table 250.66 based on service conductor size • Support for copper and aluminum service conductors • Parallel sets calculation (1-6 sets) with automatic equivalent area computation • Sole-connection exceptions per NEC 250.66(A), (B), and (C): - 250.66(A): Rod, pipe, or plate electrode - GEC capped at #6 Cu / #4 Al - 250.66(B): Concrete-encased electrode - GEC capped at #4 Cu / #4 Al - 250.66(C): Ground ring - GEC capped at #2 Cu / #2 Al • Five electrode types: Water Pipe, Rod/Pipe/Plate, Concrete-Encased, Ground Ring, Other BONDING JUMPER: • Size bonding jumpers per NEC Table 250.102(C)(1) • Same ranges as Table 250.66 for conductors within table limits • Automatic 12.5% rule for service conductors exceeding 1100 kcmil Cu or 1750 kcmil Al • Parallel sets support with combined circular mil area calculation CALCULATION RESULTS INCLUDE: • Conductor size in AWG or kcmil with alternative material • Exception applied with NEC section reference • NEC article references for every result • Detailed notes for parallel sets and electrode exceptions NEC REFERENCES INCLUDED: • NEC Table 250.122 - Equipment grounding conductor sizing • NEC 250.122(B) - EGC increase for voltage drop • NEC Table 250.66 - Grounding electrode conductor sizing • NEC 250.66(A) - Rod, pipe, or plate electrode exception • NEC 250.66(B) - Concrete-encased electrode exception • NEC 250.66(C) - Ground ring exception • NEC Table 250.102(C)(1) - Bonding jumper sizing • NEC 250.102(C)(1) - 12.5% rule for large conductors PRO FEATURES (one-time purchase): • No ads - clean interface for professionals • Save grounding calculation history with labels • Export calculations as PDF reports for permits and records • Dark theme support PERFECT FOR: • Licensed electricians sizing grounding conductors daily • Electrical apprentices and journeyman exam preparation • Electrical engineers specifying grounding systems • Electrical inspectors verifying conductor sizes OFFLINE & PRIVACY: • Works 100% offline - no internet needed on the job site • No account required • No data collection - your calculations stay on your device Simplify your grounding and bonding calculations on the job site.