Wire Voltage Drop Calculator

Calculate the two-conductor loop resistance from material, one-way cable length, and conductor area, then multiply by load current: Vdrop = I × Rloop.

For a DC two-wire cable, Rsingle = rho L/A, Rloop = 2Rsingle, Vdrop = I Rloop, Vload = Vsupply - Vdrop, and Ploss = I²Rloop.

In a two-conductor DC circuit, current travels out through one conductor and returns through the other. The total conductor length is therefore twice the one-way cable run.

One-way cable length is the physical source-to-load distance. The calculator reports total conductor length separately so the internal 2× loop convention is visible.

Loop resistance is the complete source-load-return conductor resistance. In known loop resistance mode, the entered value is already the full loop resistance and is not doubled.

Select an AWG size and material. The calculator reuses the shared AWG dataset for raw conductor area, calculates loop resistance, then applies Vdrop = I Rloop.

Larger conductor area reduces resistance and therefore reduces voltage drop for the same material, current, and cable length.

Voltage drop rises linearly with cable length. Doubling one-way cable length doubles loop resistance and voltage drop.

Voltage drop rises linearly with current. Doubling current doubles voltage drop, while wire power loss increases by four times.

Voltage drop percentage is Vdrop divided by supply voltage, multiplied by 100 percent.

Yes. This calculator defines percentage drop as Vdrop / Vsupply × 100%, not Vdrop divided by load voltage.

Subtract wire voltage drop from the source voltage: Vload = Vsupply - Vdrop.

Use Ploss = I²Rloop. The same loss also equals I × Vdrop, and the calculator verifies both identities.

Because the I²R equation contains current squared. If current doubles through the same cable resistance, heat-producing wire loss increases by four times.

Yes. Copper is available through the shared material preset data reused from the AWG reference module.

Yes. Aluminum is available as a shared material preset and produces a higher resistance than copper for the same geometry.

Yes. Metal conductor resistance generally changes with temperature. This calculator uses reference resistivity values and does not apply full temperature correction.

No. Temperature-dependent conductor resistance is reserved for WIR-011. Use suitable margin or measured resistance when conductor temperature is known.

Only as a low-frequency resistive approximation. Complete AC cable voltage drop may require reactance, power factor, skin effect, proximity effect, and conductor arrangement.

No. WIR-002 does not model three-phase voltage drop. A complete model needs resistance, reactance, phase convention, and power factor.

No. Voltage drop and ampacity are separate checks. Ampacity depends on insulation, ambient temperature, installation method, bundling, terminals, protection, and code requirements.

No. Acceptable drop depends on the system, load tolerance, regulation budget, and standards. This calculator does not declare a design safe or code compliant.

Yes. Connector, contact, switch, fuse, and terminal resistance add to the total circuit drop, but they are not included unless entered as part of known loop resistance.

That means the assumed current cannot be sustained by the simple source-and-wire model. The raw math is preserved and a model-limit warning is shown.