WireGaugeCalc Free calculator · NEC cited · works offline
Rmc Cable Size
rmc cable size is fast with WireGaugeCalc, since you enter the load amps, conductor material, and run length and the tool returns the minimum NEC gauge.
The calculator reads NEC 310.16 ampacity and the termination temperature column, so the result already matches how the breaker and lug are rated.
You get a defensible conductor size before you pull anything into the rigid metal conduit.
Open the calculatorSmallest conductor whose ampacity meets the load, NEC Table 310.16. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Conductor Material And Termination Temp Drive The Result
Copper carries more current per gauge than aluminum, so the calculator adjusts the size as soon as you switch the material.
Most lugs are rated at 75C, so the tool reads the 75C column of NEC 310.16 unless you tell it otherwise.
Because the conduit itself does not change ampacity, the gauge depends on the conductors and their terminations, not the RMC.
How The Tool Picks Your Wire Size
Give the calculator three inputs and it does the rest:
- Load in amps, taken from the breaker or the connected load
- Conductor material, copper or aluminum
- Termination temperature, usually 60C or 75C
- Number of current-carrying conductors for any derating
- Result as the minimum NEC conductor gauge
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 RMC change the wire size I need?
No, the conduit type does not change conductor ampacity. The gauge depends on the load, the conductor material, and the termination temperature, so RMC, EMT, and PVC of the same trade size all carry the same wire.
Which temperature column should I use for a 90C conductor?
You size to the lowest-rated part of the circuit, which is usually the 75C termination, even when the conductor insulation is rated 90C. Verify the lug rating and confirm the column 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.