WireGaugeCalc Free calculator · NEC cited · works offline
Nec 250.12.C.1 Bonding Jumper Sizing Calculator
nec 250.12.c.1 bonding jumper sizing calculator is fast with WireGaugeCalc, since you enter the overcurrent device rating and it returns the bonding jumper size from the NEC 250.122 table.
You pick the conductor material, so copper and aluminum are sized correctly without hand lookups.
The result gives you a defensible jumper size you can take straight to the panel.
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.
Why The Equipment Bonding Jumper Tracks The Overcurrent Device
The bonding jumper is sized from the rating of the overcurrent device ahead of it, so a larger breaker means a larger jumper.
Copper and aluminum carry current differently, so each material has its own column in the sizing table.
You get a clear number for the jumper, which keeps the equipment grounding path intact.
What The Bonding Jumper Sizing Tool Checks
Enter a few values and the tool returns the jumper size:
- Overcurrent device rating in amps
- Conductor material, copper or aluminum
- Bonding jumper size pulled from NEC 250.122
- A consistent result for raceway and equipment bonding
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 is the equipment bonding jumper sized?
The jumper is sized from the rating of the overcurrent device protecting the circuit, using the NEC 250.122 table. Larger breakers require a larger jumper, so the size scales with the device rating.
Does material change the jumper size?
Yes. Aluminum needs a larger size than copper for the same overcurrent device rating because it carries less current per gauge. Always confirm the result against the current NEC and your local authority having jurisdiction before final install.
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.