Electrical
Wire Size Calculator
Estimate the conductor size a load needs, checked against both ampacity and voltage drop.
Result
Electrical work is life-safety work governed by the NEC or your local code, and must be designed and installed by a licensed electrician. Conductor and overcurrent sizing depends on ambient temperature, conductor bundling, termination ratings, continuous-load rules and more. This is an educational estimate and must never be used as the basis for an installation. Ampacities used are NEC 310.16 at 75°C in free air conditions. Real installations require derating for ambient temperature, conduit fill and bundling, and terminations are often limited to 60°C on smaller conductors. All of which can require a larger conductor than shown.
Get a Free Business AuditQuestions
About this calculator
What size wire for a 50 amp circuit?
Ampacity tables commonly point to 6 AWG copper for 50 A at 75°C, but termination temperature ratings, derating and run length can all push that larger. A licensed electrician has to confirm it for the actual installation.
Why is voltage drop sometimes the deciding factor?
Because ampacity is about heat and drop is about distance. On a long run, the conductor that safely carries the current still delivers too little voltage at the far end.
Can I use aluminium instead of copper?
For feeders and services it is common and permitted with correct terminations and antioxidant compound. It needs roughly two sizes larger for the same ampacity and is more sensitive to loose connections.
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
Keep going
Related calculators
Voltage Drop Calculator
Calculate voltage drop over a conductor run and check it against the recommended limit..
Open calculatorBreaker Size Calculator
Work out the overcurrent protection a load needs, using the 125% continuous-load rule..
Open calculatorElectrical Load Calculator
Estimate a dwelling's electrical load and the service size it points to, using the NEC standard method..
Open calculatorEstimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.