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Calculators › Construction & Building › Cable Size / Electrical Load Calculator

Cable Size / Electrical Load Calculator

Calculate demand-adjusted electrical load, design current and approximate voltage drop, then screen common copper cable sizes for planning and discussion with a qualified electrical professional.

Enter the circuit or feeder load

Use equipment/nameplate loads where available. The cable result is a planning screen, not an installation approval.

Supply & load
Route & voltage-drop screen
Why the current-density field is editable: actual cable current-carrying capacity is not determined by conductor area alone. Installation method, insulation temperature rating, ambient temperature, grouping, thermal insulation, harmonics and other correction factors can materially change allowable current. This input is only a preliminary screening assumption.
Waiting for calculation
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Your electrical load and cable planning result will appear here after you click the button.
—demand-adjusted load
—calculated load current
—current incl. design margin
—approx. voltage drop
Minimum area from current-density screen—
Minimum area from voltage-drop screen—
Next common size screened—
Approximate drop at screened size—
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Check cable & electrical prices

After professional verification of the cable specification, carry the required size and route length into supported current price intelligence.

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Find electricians / electrical suppliers

Use the calculated load and verified cable requirement to request suitable electrical businesses and Offers.

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Important electrical safety limitation: The displayed cable size is only a mathematical planning screen. It is not a declaration that the cable is safe or compliant. Final conductor size and protective device must be verified against applicable wiring requirements and manufacturer data, including installation method, current-carrying capacity, ambient/grouping/thermal derating, voltage drop, fault current, short-circuit withstand, earth-fault protection, neutral loading, conductor material, insulation type, termination limits, earthing/bonding and coordination with the breaker/fuse. Motor and other starting loads need additional checks.

How the calculation works

Demand load = connected kW × demand factor. For single phase, current ≈ watts ÷ (voltage × power factor). For a balanced three-phase load, current ≈ watts ÷ (√3 × line voltage × power factor). The design margin is then applied. A preliminary conductor area is calculated from the editable current-density screen. A second minimum area is calculated from conductor resistivity, route length and the selected voltage-drop limit. The larger result is rounded upward to a common conductor size. Approximate voltage drop is then recalculated at that screened size.

How to Use and Check Your Result

Enter the measurements, quantities, costs and assumptions requested in the calculator above. Use its calculation control and review the displayed result. All figures should be checked against your actual project or operating conditions.

Planning and safety: Electrical or power-system sizing requires qualified design review and applicable safety standards. Finelib does not certify engineering designs or supplier quotations.

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Frequently Asked Questions

What does the Cable Size Electrical Load Calculator estimate?

It estimates planning quantities or costs from the figures you enter. Review the calculator assumptions before using the result.

Can I use this calculator for a project in Nigeria?

Yes. Enter measurements and quotations relevant to your Nigerian location and project.

Does Finelib supply current market prices automatically?

No. Prices and rates should be checked with relevant suppliers; do not assume any illustrative values are live quotations.

Are the results guaranteed to be accurate?

No. The output depends on entered assumptions and is intended for preliminary planning, not professional certification.

How should I handle wastage or losses?

Where the calculator provides a wastage or contingency field, enter an allowance appropriate to the project. Otherwise account for it separately.

Can I use the result to request supplier quotes?

Yes. Use Finelib Match to find suitable businesses and request Quotes or Offers, then verify specifications and providers.

Should a professional review the result?

Yes, when the decision involves structural safety, electrical safety, major equipment, significant expenditure or regulatory requirements.