About JobWireCalc

Who it is for

It is for the person on a ladder, in a truck, or at a panel who wants a fast check of voltage drop, wire size, conduit fill, or box fill before opening the code book. Apprentices can use it to see the arithmetic. It is not a training program and it does not sign your permit.

What the tools do

Each calculator runs in your browser. Voltage drop uses the common approximate formulas with K = 12.9 for copper and K = 21.2 for aluminum. Wire size walks a short table of orientation ampacities and the usual small-conductor overcurrent ceilings. Box fill counts volume allowances for one wire size. Conduit fill multiplies approximate conductor area by the count and compares it with 53%, 31%, or 40% of an approximate raceway area.

What it is not

• Not affiliated with NFPA, and not an official or certified NEC product.
• Not a substitute for the code edition adopted where you are working.
• Not a design, a load calculation, or a stamped engineering judgment.
• Not a promise that an inspector will accept the result.

Treat every number as an estimate. Read the limits on the tool page, then check the book and the authority having jurisdiction.