WireGaugeCalc Free calculator · NEC cited · works offline
Residential Load Calculator
residential load calculator is simple to run with WireGaugeCalc, since the app follows the NEC standard dwelling method.
You enter square footage, appliance loads, and HVAC, so the calculator totals the demand and the service size.
That gives you the amperage a home actually draws.
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 Dwelling Load Adds Up
General lighting starts at 3 VA per square foot, so the floor area sets the base load.
Small appliance and laundry circuits add fixed amounts, and demand factors then reduce the total.
The calculator applies the larger of heating or cooling, since they rarely run at the same time.
What The Calculator Counts
The dwelling total comes from several load groups:
- General lighting at 3 VA per square foot
- Two small appliance circuits and one laundry circuit
- Fixed appliances like the range, dryer, and water heater
- The larger of heating or air conditioning
- Demand factors that scale the first 10 kVA differently
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
Does this use the standard or optional method?
The calculator follows the NEC standard dwelling method with its demand factors. For the optional method or unusual loads, verify against the current NEC and your local authority having jurisdiction.
Do I count both heating and cooling?
No, you take the larger of the two, since heating and air conditioning are not expected to operate together. The calculator picks the controlling load for you.
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.