AutoCAD Electrical,
without the $1,900/year.
Free browser-based electrical wiring diagram editor. Live NEC auditing, box fill calculator, conduit fill calculator. No install, no account.
Live NEC Auditing
Code checks that run as you draw.
Every wire and device you place is evaluated against NEC requirements in real time. Issues appear as warning badges in the diagram — before you close the walls.
Open editor free →-
Breaker Overload — NEC 210.20Sums load current per circuit, flags every breaker where load exceeds the rating. Cycle-safe graph traversal catches loops.
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GFCI / AFCI Coverage — NEC 210.8 / 210.12Traces upstream for GFCI and AFCI breakers. Flags outlets in required locations that lack protection.
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Neutral at Switch — NEC 404.2(C)Detects smart switches requiring a neutral and flags the location when no neutral conductor is connected.
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Voltage Drop — VD = (2×12.9×I×L)/CMCalculates drop per wire segment. K = 12.9 copper at 75°C. Highlights segments above the NEC 3% informational limit.
Pro Feature
Draw over the architect's floor plan.
Got a floor plan from the architect or a scanned sketch? Export it as PNG, drop it into DesignedWire, and draw your electrical circuit on top. The floor plan appears as a dimmed, locked background — your symbols and wires go on top, then export the whole thing as PDF or PNG.
No separate CAD layer system. No scaling setup. Drop the image in, adjust opacity with a slider, draw. Estimators use this to mark up a plan set before sending to the field. Contractors use it for permit drawings when the AHJ wants the circuit shown on the floor plan.
Electrical circuit drawn over a floor plan — Pro feature
Free Calculators
Every NEC calculation, right here.
Standalone free calculators — no diagram required. Use on the job, in the office, or during exam prep.
Box Fill Calculator
Conductors, device yokes (2×), internal clamps, equipment grounds. Instant in³ total with pass/fail.
Open calculator →Conduit Fill Calculator
EMT, IMC, RMC, PVC. Mixed sizes using Tables 4 and 5. Instant fill % with pass/fail.
Open calculator →Thermostat Checker
Select wire colors and HVAC type — instantly see which terminals match and which smart thermostats are compatible.
Open checker →Residential Load Calculation
Service upgrade, EV charger permit, panel replacement — calculate required ampacity using the standard method with demand factors.
Open calculator →NEC Wiring Guides
Deep guides. Not thin content.
2,000–4,200 words each. NEC-grounded prose, interactive diagrams, worked examples, HowTo and FAQPage schema for every page.
3-Way Switch Wiring Diagram
SPDT switches, traveler wires, NEC 404.2, step-by-step install, 4-way extension, smart switch wiring, troubleshooting.
Read guide →Smart Switch Neutral Wire
Why smart switches need a neutral, switch loops, NEC 404.2(C), no-neutral options, brand comparison table.
Read guide →GFCI and AFCI Requirements
Room-by-room NEC 210.8 and 210.12 breakdown for the 2023 NEC, dual-function breaker guide, room grid.
Read guide →Voltage Drop Formula
VD = (2×K×I×L)/CM fully explained. K = 12.9 sourced. Worked examples for bedroom, workshop, and EV charger.
Read guide →Box Fill — NEC 314.16 Guide
Counting rules, Table 314.16(B) by gauge, device yoke double allowance, worked examples for 3 box types.
Read guide →Conduit Fill — NEC Ch.9 Guide
40%/31%/53% rules. Tables 1, 4, 5 explained. EMT vs IMC vs RMC. Mixed-conductor worked examples.
Read guide →Single-Line Diagram Guide
When you need an SLD, what it must contain, and how to draw one for service upgrades, EV charger permits, and panel replacements.
Read guide →Pre-built Templates
Start from a working diagram.
One click to open a fully wired template in the editor. Add load values, run the NEC audit, export to PDF.
3-Way Switch
Two switches, traveler wires, light fixture, neutral at both switch locations.
4-Way Switch
Three-location control — two 3-way switches + one 4-way in the middle.
GFCI Outlet
Kitchen or bathroom circuit with GFCI protecting downstream receptacles.
Panel Schedule
200A residential panel with labeled breakers and load columns.
EV Charger Circuit
240V EVSE circuit with NEC 625.41 125% continuous load sizing.
Smart Switch (3-Way)
Main smart dimmer + companion with neutral at both boxes.
Fire Alarm Riser
FACP, pull stations, horn/strobe, initiating and notification circuits.
Access Control Door
Card reader, door strike, REX, access control panel and power supply.
Structured Cabling
Patch panel, data jacks, horizontal cabling with TIA-568 labeling.
Generator Transfer Switch
ATS with utility and generator sources, critical load panel.
Pricing
Free for residential. Pro for commercial.
AutoCAD Electrical runs $1,900/year. Visio runs $580/year. DesignedWire is free for residential — no account, no install. Pro is $59/year for commercial symbols and templates.
No account. No time limit. Full editor and all NEC calculators.
- Full wiring diagram editor
- Residential symbol library
- NEC breaker overload audit
- GFCI / AFCI coverage audit
- Neutral-at-switch audit
- Voltage drop per wire segment
- Box fill calculator — NEC 314.16
- Conduit fill calculator — NEC Ch.9
- Thermostat compatibility checker
- QR share links
- PNG and PDF export
Full Pro access for one day. No subscription, no commitment — pay once and go.
- Everything in Free
- Commercial symbol library
- All Pro templates
- Floor plan image underlay
- Priority support
Everything in Free, plus commercial symbols, floor plan underlay, and advanced templates.
- Everything in Free
- Fire alarm symbols (FACP, pull station, horn/strobe)
- Access control symbols (card reader, door strike)
- Structured cabling symbols
- Fire alarm riser template
- Access control door template
- Structured cabling template
- Generator transfer switch template
- Floor plan underlay (PNG/JPG over diagram)
- Priority support
| Feature | DesignedWire | draw.io / Google Drawings | Visio $580/yr | AutoCAD Electrical $1,900/yr |
|---|---|---|---|---|
| Price | Free / $59 yr | Free | $580/yr | $1,900/yr |
| No install required | ✓ Browser | ✓ Browser | ✗ Install | ✗ Install |
| Electrical symbols | ✓ NEC residential + commercial | Generic only | Basic | ✓ 65,000+ |
| Live NEC auditing | ✓ Built in | ✗ | ✗ | Partial |
| Box fill calculator | ✓ Free | ✗ | ✗ | ✗ |
| Conduit fill calculator | ✓ Free | ✗ | ✗ | ✗ |
| Floor plan overlay | ✓ Pro ($59/yr) | Manual workaround | ✓ | ✓ |
| QR share link | ✓ Free | ✗ | ✗ | ✗ |
| PDF export | ✓ Free | ✓ | ✓ | ✓ |
| Learning curve | Minutes | Minutes | Days | Weeks |
FAQ
Common questions.
Is DesignedWire free?
Yes. Full editor, all NEC calculators, QR share, PNG/PDF export — no account, no download, no time limit. Day Pass ($4.99) unlocks all Pro features for 24 hours with no subscription. Pro ($59/year) adds commercial symbols, fire alarm and access control templates, and floor plan image underlay (drop a PNG/JPG floor plan behind your diagram and draw on top).
Does DesignedWire require a download or account?
No download, no account. Open it in Chrome or Safari on any device and start drawing immediately. Diagrams are saved in browser local storage, or share via QR/URL to any device.
How does the NEC audit work?
DesignedWire traces the topology of your diagram as a graph. Breaker overload sums load current per circuit. GFCI/AFCI audit traces upstream for protection devices. Neutral audit checks smart switch nodes. Voltage drop runs VD = (2×K×I×L)/CM per labeled wire segment.
What is the box fill calculation per NEC 314.16?
Count allowances: each insulated conductor entering or leaving the box (1 each) + all equipment grounding conductors combined (1 allowance for the largest) + all internal clamps combined (1 allowance) + each device yoke such as a switch or receptacle (2 allowances based on largest conductor connected). Multiply by the in³ value from Table 314.16(B) for the largest conductor. Compare to box marked capacity.
Can I draw a wiring diagram over a floor plan?
Yes — with a Pro plan or Day Pass. Drop a PNG or JPG floor plan into the editor and it appears as a dimmed, locked background. Draw your electrical symbols on top, adjust opacity with a slider, then export the whole thing as PNG, SVG, or PDF. The floor plan stays in the export. Most people export the architect's PDF floor plan page as a PNG first, then drop that in.
What is the 40% conduit fill rule?
NEC Chapter 9, Table 1 limits conductor fill to 40% of the conduit's cross-sectional area when 3 or more conductors are present (31% for 2, 53% for 1). For mixed sizes, sum individual conductor areas from Table 5 and compare against the 40% fill area from Table 4 for your conduit type and trade size.
Ready for your next diagram?
Open DesignedWire in your browser. No account, no download, no friction.