Quick start
- Enter source voltage, current amps, and one-way length.
- Enter the maximum voltage-drop percentage.
- Choose single/DC or three-phase circuit type.
Best uses
These are the situations this tool is meant for. If your task is close to one of these, the examples and notes below can help you choose the right inputs.
- Estimate copper AWG size for a voltage-drop target.
- Compare branch-circuit and longer-run examples.
- See estimated voltage drop and load voltage together.
- Learn why current and length affect conductor choice.
What this calculator is solving
The Wire Size Calculator tests common copper AWG sizes and returns the first size that stays within the voltage-drop percentage you choose. It is a planning helper, not an electrical-code sizing tool.
You do not need to memorize the formula first. Start by matching each input label on the calculator to the number, date, unit, or setting you actually have.
The formula in plain language
In plain language: The calculator tests common copper AWG sizes and returns the first size whose estimated voltage drop is within the selected percentage. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
If that sounds abstract, use the example cards on the calculator page. They show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the headline result first. Then look at the smaller supporting lines because they explain the parts behind the answer, such as totals, units, ranges, or formula steps.
- The main answer is the first common copper AWG size that meets the voltage-drop target.
- Estimated drop and percent drop show why the size was selected.
- Load voltage shows source voltage after the estimated drop.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: the wrong unit, date, weight, scale, mode, or policy assumption.
- Do not treat voltage drop as the only wire-sizing rule.
- Do not ignore ampacity, insulation, raceway, temperature, material, and local code.
- Do not use this as a substitute for a licensed electrician.
Research and references
These references shaped the calculator assumptions, unit choices, or safety notes.
Examples from the calculator
12 AWG copper estimate
Estimated AWG size
Estimated AWG size
FAQ in plain language
When should I use the Wire Size Calculator?
Use it when your task matches one of these common needs: Estimate copper AWG size for a voltage-drop target. Compare branch-circuit and longer-run examples. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Wire Size Calculator doing with my inputs?
In plain language: The calculator tests common copper AWG sizes and returns the first size whose estimated voltage drop is within the selected percentage. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What do the main Wire Size Calculator inputs mean?
Source voltage: voltage before the wire run loses voltage. Current amps: load current for the voltage-drop estimate. One-way length: distance from source to load. Max voltage drop: the target percentage the estimate tries to stay under.
How should I read the Wire Size Calculator answer?
Read the main answer first, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the answer?
This is not a code-complete wire sizing tool. Ampacity, insulation rating, terminals, raceway, temperature, material, and local code must be checked separately. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Is this the same as an electrical code wire-size chart?
No. This estimates voltage drop only. Real wire sizing also needs ampacity, conductor insulation, raceway fill, terminals, temperature, material, and local code rules.
Related tools
- Wire Resistance Calculator Estimate copper wire resistance from AWG size, length, and conductor count.
- Voltage Drop Calculator Estimate voltage drop from current, wire length, voltage, phase, and copper AWG size.
- Electricity Calculator Estimate electricity use and cost from watts, hours, days, and rate per kWh.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to paste the expression and result into notes, homework, a message, or another document. Check the units and assumptions before copying.