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Can I use this result for planning?

Yes, but treat it as a starting point and compare it with your real situation before making a final decision.

What should I do after using the Cable Size Calculator?

Review the explanation, test one alternative scenario, and use the result as a starting point before making your final decision.

Why does this page include guidance below the tool?

The guidance helps you understand the result, avoid common mistakes, and choose a practical next step instead of only seeing a number.

Home / Engineering Intelligence / Electrical Engineering Intelligence / Cable Size Calculator

Cable Size Calculator

Calculate Electrical Engineering Intelligence

Estimate required cable cross-section from current, length, voltage drop target, and material assumptions.

Cable size calculator

Get the answer first

Estimate a starting cable size before code-compliant electrical design.

EnterCurrent amps, Cable length m, Allowed drop %
CalculateExample: 30 A, 25 m, 3% drop, and 230 V estimates about 3.80 square mm by the simplified copper formula.
DecideCompare voltage drop, circuit load, and electrical current calculators.

Start calculator

Example

Example: 30 A, 25 m, 3% drop, and 230 V estimates about 3.80 square mm by the simplified copper formula.

Avoid this mistake

Cable sizing must follow code, ampacity tables, insulation, temperature, installation method, voltage drop, short-circuit protection, and qualified electrician review.

Related path

Pick the right calculator path

Use these guided hubs when the calculator result points to a bigger decision or a related search intent.

Electrical Calculator Hub Use Ohm law, wattage, voltage drop, load, wire, power, and electrical planning calculators with safety-aware guidance.

Electrical engineering safety note

Electrical engineering calculators on ToolsBing are preliminary educational and planning tools only. Electrical work can create shock, fire, arc-flash, equipment damage, and code-compliance risks. Verify all calculations with licensed electricians, qualified engineers, manufacturer data, local electrical codes, protective-device requirements, and safety standards before installation or operation.

Enter electrical engineering inputs

Current AOne-way Length mAllowable Voltage Drop %System Voltage V

Estimated result

ResultWaiting for input

mm² estimate

ConfidencePlanning estimate

Use for education, early planning, and comparison only.

Next stepCheck code and protection

Verify conductor ratings, breaker/fuse sizing, derating, grounding, environment, and local code requirements.

Formula and assumptions

Required conductor area estimate is based on current, distance, voltage, and allowable drop

This calculator uses simplified electrical assumptions. Real systems may require derating, conductor temperature ratings, insulation type, installation method, short-circuit protection, coordination studies, power quality review, and licensed professional verification.

Related electrical calculators

Next useful step

Use the result without guessing

Before you act, run one real scenario and one conservative scenario.

Refine inputsReplace the example with your real values. Check methodSee what the calculator includes and leaves out.

Watch forCable sizing must follow code, ampacity tables, insulation, temperature, installation method, voltage drop, short-circuit protection, and qualified.

Known input

30 A load, 25 m one-way run, 3% voltage-drop target on a 230 V circuit.

Expected result

Displayed simplified copper area estimate should be about 3.80 square mm.

Method check

Area estimate = 2 x current x length x copper resistivity / allowed voltage drop. Use as a screening check only; code ampacity and installation derating control final sizing.

Related path

Continue with a focused hub

Use these guided hubs when the calculator result points to a bigger decision or a related search intent.

Electrical Calculator Hub Use Ohm law, wattage, voltage drop, load, wire, power, and electrical planning calculators with safety-aware guidance.

Check before using this result

Verify the inputs, units, assumptions, and any local rules that apply. For financial, health, engineering, or construction decisions, confirm the result with a qualified professional or an authoritative source.