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Everything you need to master the NEC and pass your exam
- Unlimited NEC code questions
- 1,200+ practice exam questions
- All field calculators
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- 4 NEC code years (2017, 2020, 2023, 2026)
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Sparky knows the NEC code. Ask about code requirements, wire sizing, GFCI rules — anything on the job site.
Tools
Quick helpers for common NEC tasks.
Conduit Fill
Estimate conduit fill for common raceways.
Wire Sizing
Suggest conductor and breaker sizes for feeders/branches.
Conduit Bend Calculator
Offsets, saddles, 90° bends — mark points and diagram per bender.
Box Fill Calculator
Compute box volume and find a suitable box per 314.16.
Load Calculator
Rough load calculations for services and feeders.
NEC Quick Reference
Jumping-off points for common NEC articles.
Voltage Drop
Calculate voltage drop for any run. Know when to upsize wire.
Box Fill Calculator
Based on NEC 314.16. Enter conductors by gauge, devices, and equipment grounds to estimate required volume.
Box Fill Preview
How it works
This tool applies NEC 314.16 box fill rules by converting conductors, devices, and grounds into equivalent conductor counts and multiplying by the volume allowance for the largest gauge present. The suggested box volume is then compared with common box sizes—always verify against the actual cubic-inch marking and the full Code text.
Wire Sizing
Quick reference based on NEC Table 310.16 (general 60–75 °C ampacity; always verify final sizing).
Wire Cross-Section
How it works
This calculator references typical ampacity values from NEC Table 310.16 for copper and aluminum conductors at 60–75 °C. It selects the smallest conductor with an ampacity at or above the entered load; you still need to apply temperature limitations, adjustment/correction factors, and any specific Code notes for the installation.
Conduit Fill
Uses NEC Chapter 9, Tables 4 & 5 for raceway fill (40% limit for 3+ conductors).
Conduit Cross-Section
How it works
Conduit fill is checked against the 40% maximum fill area from NEC Chapter 9, Table 1 and the raceway tables for each conduit type. This tool uses representative areas for common conduit sizes and THHN conductors—always confirm final values with the exact Chapter 9 tables and manufacturer data.
Load Calculator
Rough dwelling-unit load per NEC 220 (3 VA/ft² lighting, 1500 VA for each small-appliance and laundry circuit, plus fixed appliances).
How it works
This dwelling load estimate follows NEC 220 principles using 3 VA/ft² for general lighting and receptacles, 1500 VA for each small-appliance and laundry circuit, plus listed fixed appliances. It produces a ballpark amp value and service size; a full Article 220 calculation and local amendments still govern the actual installation.
NEC Quick Reference
Search plain-language summaries of commonly used NEC articles.
How it works
These summaries highlight high-traffic NEC articles in plain language so you can quickly recall what each section covers. Always read the actual article text and any local amendments before making a final code decision.
Photo Analyzer
Upload a photo of your work, a wiring diagram, or a panel — Sparky will explain it and reference the relevant NEC articles.
Tap to take a photo or upload one
Works with wiring diagrams, panels, homework assignments
How it works
Upload a photo and Sparky looks at it — he identifies wiring, equipment, diagrams, or assignment questions, then gives you a practical explanation with relevant NEC references. Subscribers only.
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Voltage Drop
Calculate voltage drop for a circuit run. NEC recommends max 3% on branch circuits, 5% total.
How it works
Uses the standard VD formula: VD = (2 × K × I × D) / CM for single phase, adjusted for three phase. K is the resistivity constant for the conductor material, CM is the circular mil area of the wire. NEC informational note recommends keeping branch circuit drop under 3% and total drop (feeder + branch) under 5%.
Conduit Bend Calculator
Offsets, saddles, 90° bends — enter measurements and see the diagram. Supports Klein, Greenlee, Ideal, Rigid, and more.