Electrician Helper: NEC Calc

Electric Helper is the field calculator built for working electricians. Every answer is big enough to read from arm's length, cites the NEC table it came from, and shows the math behind it so you can defend it to an inspector.

WHAT YOU CAN DO
• Wire size and ampacity: Table 310.16 with ambient temperature correction, bundling adjustment, 110.14(C) termination limits, the 240.4(D) small-conductor rule and a breaker recommendation. Or pick a size and see what it can carry.
• Voltage drop: DC, single-phase and three-phase, copper or aluminum, parallel sets, Table 8 resistance or Table 9 AC impedance with power factor. Find the drop, the minimum size for 3 %, or the maximum run length.
• Conduit fill: EMT, IMC, RMC, PVC 40/80, FMC, LFMC, LFNC and ENT with Chapter 9 Tables 1, 4, 5 and 8. Mix sizes and insulation types, include bare grounds, handle nipples. Get fill %, the smallest conduit that works, or the most conductors that fit.
• Box fill: 314.16 volume counting for conductors, devices, clamps, fittings and grounding conductors, with the smallest standard box that fits.
• Grounding: equipment grounding conductors from Table 250.122 with the 250.122(B) upsizing rule, and grounding electrode conductors from Table 250.66.
• Motors: full-load current from Tables 430.248 and 430.250, conductor sizing, branch-circuit protection per Table 430.52 for fuses and breakers, and overload settings.
• Transformers: primary and secondary current plus overcurrent protection per Table 450.3(B).
• Dwelling load: standard and optional methods from Article 220, ranges, dryers, appliances, heat versus air conditioning, EV chargers, and the resulting service size. Share the full step list with the inspector.
• Conduit bending: offsets, three-point and four-point saddles, 90° stubs and back-to-back bends with numbered marks measured from the end of the pipe, shrink, and bender take-up.
• Basics: Ohm's law wheel and power / kVA with power factor.
• Quick references: ampacity tables, AWG to mm² and resistance, standard breaker sizes, bend multipliers, NEMA plug and receptacle configurations, and wire color codes for the US, Canada, IEC and UK.

BUILT FOR THE JOBSITE
• Large type and large touch targets that work with gloves and in sunlight.
• Light and dark mode plus seven color themes, including high-contrast options for dim electrical rooms.
• Enter lengths the way the trade does: 12-3/8 or 2' 6", with a fraction bar for sixteenths. Metric available.
• Choose your code edition: NEC 2017, 2020, 2023 or 2026. Edition-specific rules such as EV charger loads and box-fill counting follow your choice. All editions are included.
• Every result has a "Show work" panel with the formula, the values used and the code section.
• Copy or share any result as text.
• Favorites and recents put your everyday tools one tap away.

NO STRINGS
• Works completely offline.
• No ads, no account, no subscription for the math.

Electric Helper is a reference tool. Results are based on published code tables and standard formulas; the adopted code and the authority having jurisdiction govern the installation. NEC and National Electrical Code are trademarks of the National Fire Protection Association, which is not affiliated with this app.

Questions or requests: support@criosoft.com

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