WireGaugeCalc Free calculator · NEC cited · works offline
Nec 220.12.C.1 Sizing Calculator
Nec 220.12.c.1 sizing calculator is simple with WireGaugeCalc, since the app applies the general lighting load per area and then the demand factors.
You enter the occupancy type and square footage, and the app computes the connected lighting load in volt-amperes.
You see the demand load in seconds, so you can size the feeder and service from the result.
Open the calculatorEnter any two values and read the rest.
Ohm’s law: V = I × R and P = V × I. Field aid only, verify against the current NEC and your local authority having jurisdiction.
How the general lighting load is calculated by occupancy
Each occupancy has a unit load per square foot, so the connected lighting total tracks the floor area.
The app multiplies area by that unit load, since that sets the base volt-ampere figure.
Demand factors then trim the total, because not all lighting runs at full load at once.
What drives the general lighting load total
The calculator uses a few inputs to reach the demand load:
- Occupancy type, which sets the VA per square foot
- Total floor area in square feet
- Connected lighting load before demand
- Applicable demand factor for the occupancy
- Feeder or service rating the result feeds into
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Which unit load applies to my building?
The unit load depends on occupancy type, so a dwelling, office, or store each use a different VA per square foot. Verify the exact value against the current NEC and your local authority having jurisdiction.
When can I apply a lighting demand factor?
Demand factors apply once the connected lighting load is known, and they vary by occupancy and load range. The calculator applies the matching factor so the demand load is ready for feeder sizing.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.