WireGaugeCalc Free calculator · NEC cited · works offline
Ohm Law Calc
Ohm law calc is fast with WireGaugeCalc.
You enter any two of voltage, current, and resistance, and the calculator solves the third using V equals I times R.
So you check a load, a resistor, or a circuit value without doing the math by hand.
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.
From Ohm's Law To A Voltage Drop Calculator
Since voltage equals current times resistance, a small wire resistance over a long run shows up as real voltage loss.
That same math feeds an Ohm's law calculator voltage drop check, where conductor resistance and current set the drop along the run.
The calculator keeps the units straight so the result is usable on the spot.
What You Can Solve With Ohm's Law
Enter two known values and the calculator returns:
- Voltage from current times resistance
- Current from voltage divided by resistance
- Resistance from voltage divided by current
- Power when you add P equals V times I
- Voltage drop across a known conductor 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
How does Ohm's law connect to voltage drop?
Voltage drop is current multiplied by the conductor's resistance, which is Ohm's law applied along the run. Longer runs and higher current raise the drop, so the same equation tells you when to upsize the wire.
Can I get power from the same values?
Yes, power is voltage times current, so once you have two of the three Ohm's law values you can find watts too. For sizing decisions based on the result, verify against the current NEC and your local authority having jurisdiction.
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.