Cable Sizing Calculator
Wire size from current and voltage drop
Cable Sizing Calculator turns wire size from current and voltage drop into an instant, step-by-step result. Fill in Current (A), Cable Length (m) and Max Voltage Drop (%) and read your answer immediately. The result comes with a step-by-step breakdown — no black box, just math you can check. Great when you want certainty fast — no formulas to memorize, no apps to install. Privacy-first: the calculation is local, your data stays yours, and the tool keeps working offline. It is part of the Engineering collection on CalcProMaster, alongside cable sizing calculator wire ampacity voltage drop, free online cable sizing calculator and more. Open Cable Sizing Calculator, enter your numbers, and you will have a trustworthy answer before you know it.
What does the page calculator do?
Cable Sizing Calculator works out the min area from the Current, Cable Length, and Max Voltage Drop, following standard Engineering conventions — the page defaults produce a min area of 5.0 mm².
- Inputs: Current, Cable Length, and Max Voltage Drop.
- Output: the min area, plus the intermediate steps behind it.
- Method: the standard Engineering formula, evaluated entirely in your browser.
Quick answer
With the default inputs (current of 20, cable length of 50, max voltage drop of 3), cable sizing calculator returns a min area of 5.0 mm². Assumptions and limits are summarized below.
How does the Cable Sizing Calculator work?
Cable Sizing Calculator computes the min area directly from your inputs — the Current, Cable Length, and Max Voltage Drop feed the formula. Nothing is uploaded: the math runs locally in your browser and the result appears as you type.
How it works
At its core, Cable Sizing Calculator takes the Current, Cable Length, and Max Voltage Drop and evaluates the standard formula step by step, so the figure can be checked rather than trusted on faith.
Using the Cable Sizing Calculator
- Current — the value that feeds directly into the formula — match it to the scenario you are modeling before moving on.
- Cable Length — one of the values the calculation builds from; the result reflects exactly what you type here.
- Max Voltage Drop — used in the first stage of the calculation, so entering it accurately matters more than any later refinement.
- The output panel in cable sizing calculator leads with the headline result and follows with the steps behind it, so the value can be checked rather than assumed.
- Iterate. Vary the inputs one at a time; the movement in the figure shows which lever matters most for your cable sizing question.
The formula behind the result
Cable Sizing Calculator lists every intermediate step in the result panel, so the derivation of the figure can be checked line by line.
Worked example: with current of 20, cable length of 50, max voltage drop of 3, this cable sizing calculation returns Min area: 5.0 mm². The same run reports Max R = 0.3450 Ω | Drop ≤ 6.9 V.
The steps it follows:
- Max drop = 230 × 3% = 6.9 V
- Max resistance = 6.9/20 = 0.3450 Ω
- Copper ρ = 0.0172 Ω·mm²/m
- Area = ρ×L×2/R = 5.0 mm²
Substitute your own values and the same steps produce your answer — that is the point of a calculator that shows its working.
Understanding the result
Interpret the min area against the inputs that produced it — the same number from different inputs can mean different things, which is why the pairing is always shown.
Where it helps
Typical uses for Cable Sizing Calculator include planning around a target figure, comparing scenarios side by side, and double-checking the min area — anywhere the figure needs to be defensible rather than guessed.
Common mistakes
The most common error with Cable Sizing Calculator is a unit mismatch — one value entered in different units than its label assumes quietly skews the result. Check each label before typing.
Tip: Run Cable Sizing Calculator twice with deliberately low and high inputs; the spread tells you how sensitive the figure is, which a single run never shows.
Assumptions and limitations
Results from Cable Sizing Calculator are estimates computed from the values entered; real-world outcomes can differ when fees, taxes, or conditions not modeled here apply.
Why use this calculator
Because the page doubles as documentation: Cable Sizing Calculator puts the formula, a worked example, and the assumptions right beside the calculator.
From Our Guides Library
Frequently Asked Questions
What does the tool calculate?
Cable Sizing Calculator keeps the whole calculation in front of you — the Current, Cable Length, and Max Voltage Drop, the formula, the intermediate steps, and a worked example you can reproduce line by line. Because the working is visible: Cable Sizing Calculator shows each operation behind the figure in the steps panel, so you can verify the result instead of trusting a black box.
How is the min area calculated?
The first steps are max drop = 230 × 3% = 6.9 v, then max resistance = 6.9/20 = 0.3450 ω. The calculation in Cable Sizing Calculator applies the standard Engineering method, keeping full precision internally and rounding only the final display.
What do I need to use the Cable Sizing Calculator?
The Current, Cable Length, and Max Voltage Drop it asks for, or the page defaults if you just want to see the calculation work. Each input maps directly to the formula, and changing any one of them recalculates the min area instantly.
What does the result from the tool mean?
The main number the cable sizing calculator returns is the min area for your exact inputs, and the supporting figures and step list give it context. Cable Sizing Calculator assumes the units shown in each label — entering values in different units will skew the result proportionally.
When is the page most useful?
Common scenarios for Cable Sizing Calculator: planning around a target figure, comparing scenarios side by side, and double-checking the min area. The step list makes it equally useful for learning the method and for double-checking someone else's numbers. Run Cable Sizing Calculator twice with deliberately low and high inputs; the spread tells you how sensitive the min area is, which a single run never shows.