Voltage drop sizing tool
Wire gauge calculator
Estimate the copper or aluminum conductor cross-section required to meet a voltage-drop target, or check the drop of a known metric size. The model supports DC, single-phase AC and balanced three-phase AC runs with temperature-adjusted resistivity.
Required conductor area
Calculated minimum
11.65 mm²
Next metric size
16 mm²
Approximate AWG
6 AWG
Area comparison only
Drop at metric size
524.19 mV
2.184%
Estimated load voltage
23.476 V
Conductor loss
5.24 W
Selection check still required
- Voltage-drop sizing does not verify ampacity, insulation rating, installation method, grouping, harmonics or fault protection.
American Wire Gauge size reference
Select a gauge to compare its nominal bare-conductor diameter and cross-sectional area. Dot size follows conductor diameter so the AWG progression is visible at a glance.
Selected 7 AWG: 3.665 millimeter diameter and 10.549 square millimeter area.
How to size a conductor by voltage drop
Use the source-to-load distance and operating current, then treat the result as one input to a complete cable-selection check.
- 01
Choose the circuit system
Select DC, single-phase AC or balanced three-phase AC. For three-phase circuits, enter line-to-line voltage and line current.
- 02
Enter the real circuit conditions
Enter load current, one-way cable length, conductor material and a realistic conductor operating temperature.
- 03
Size or check the conductor
Size mode finds the minimum area for a voltage-drop target and rounds up to a common metric size. Check mode evaluates an area you already know.
- 04
Complete the safety checks
Verify ampacity, insulation, installation method, grouping, harmonics, short-circuit withstand, protective devices and local code separately.
Voltage-drop sizing model
The calculator uses conductor resistance and a simplified unity-power-factor circuit model. Cable reactance is not included.
Temperature-adjusted resistivity
ρT = ρ20 × [1 + α20(T − 20 °C)]
Required cross-section
A = kρTLI / ΔVmax
Estimated voltage drop
ΔV = kIρTL / A
Voltage drop percentage
ΔV% = 100 × ΔV / Vsystem
Circuit factor
k = 2 for DC or single-phase; k = √3 for balanced three-phase
Length is the one-way source-to-load distance. The factor accounts for the return conductor in DC and single-phase circuits, or the line-to-line relationship in a balanced three-phase circuit. Copper and aluminum resistivity are adjusted from 20 °C reference values. The rounded metric recommendation is the next area in the tool's common-size table; the AWG result is only an approximate area comparison.
Voltage drop alone never establishes a safe conductor size. The selected cable must also satisfy the applicable electrical code and manufacturer data for ampacity, conductor and insulation temperature, installation method, ambient temperature, grouping, terminals, harmonics, fault current, protective-device operation and mechanical requirements. AC power-factor loads and larger cables may require resistance-and-reactance data from the cable manufacturer.
Checks before choosing a cable
Use the calculated area as a voltage-drop constraint, then select the actual cable from verified installation data.
Verify current-carrying capacity
Choose a cable whose corrected ampacity meets the design current after applying the required ambient, grouping and installation-method factors.
Use a realistic conductor temperature
Resistance rises with conductor temperature. A 20 °C calculation can understate operating voltage drop when the cable runs hot.
Use cable impedance for AC loads
For low power factor, large conductors or long AC runs, inductive reactance can materially affect voltage drop. Use manufacturer R and X data and the full AC equation.
Check starting and transient current
Motors, solenoids and other loads can draw substantially more current during starting. Confirm that temporary voltage drop will not cause malfunction or contactor dropout.
Coordinate protection and fault loop
Confirm short-circuit withstand, earth-fault loop impedance and protective-device disconnection time independently of normal-load voltage drop.
Confirm terminal compatibility
Check conductor material, strand class, lug range, tightening requirements and any aluminum-conductor preparation specified by the equipment manufacturer.
Wire gauge calculator questions
Should I enter one-way or round-trip wire length?
Enter the one-way source-to-load distance. The calculator applies the two-conductor factor for DC and single-phase circuits, or the square-root-of-three factor for a balanced three-phase circuit.
Does the calculated wire size have enough ampacity?
Not necessarily. This result is based only on voltage drop. Ampacity depends on the governing code, conductor insulation, ambient temperature, installation method, grouping and other conditions.
Why does conductor temperature change the result?
Metal resistance increases as temperature rises. A hotter conductor therefore produces more voltage drop and power loss for the same length, current and cross-section.
Is the AWG result an exact equivalent to the metric size?
No. AWG and metric conductor series use different nominal areas. The tool reports the smallest listed AWG area that is not below the calculated area, for comparison only.
What assumptions are used for three-phase circuits?
The simplified result assumes a balanced circuit, line-to-line voltage, line current, unity power factor and negligible cable reactance. Use cable impedance data for a detailed AC calculation.
Related engineering tools
Voltage divider calculator
Calculate voltage relationships in low-power resistive circuits and check loading effects.
Open resource
Reactance calculator
Explore frequency-dependent impedance before applying a more detailed AC cable model.
Open resource
Low-pass and high-pass filter calculator
Calculate first-order impedance and frequency relationships for passive networks.
Open resourceAll engineering tools
Browse Xindustra’s electrical, timing, component and RF calculators.
Open resource