WireGaugeCalc Free calculator · NEC cited · works offline
Free Online Electrical Calculator
Free online electrical calculator is fast with WireGaugeCalc, since it opens in any browser at no cost.
The app works the common NEC math, from wire size to voltage drop to conduit fill.
That means you check a circuit from the field without buying or installing software.
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.
What WireGaugeCalc Does in the Browser
You enter load, distance, or conductor counts, so the tool returns the matching NEC result.
Each calculator names the rule it uses, since the rule decides the answer.
Nothing is stored behind a paywall, as the tool stays free to run.
Calculations You Can Run Online
One page gives you the math electricians reach for most:
- Wire size for a given load
- Voltage drop over a run length
- Conduit fill at the 40% limit
- Box fill by NEC 314.16(B)
- Ampacity by temperature column
- Ohm's law for current and resistance
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 the online calculator follow the NEC?
Yes, each tool uses the relevant NEC table or formula, such as 310.16 for ampacity. Confirm any result against the current NEC and your local authority having jurisdiction before final work.
Can I use it on a phone in the field?
Yes, WireGaugeCalc runs in a mobile browser, so you can calculate on site. There is no install and no fee to use it.
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.