Voltage Drop Calculator

Estimate voltage drop by NEC data (R + X by conduit), Estimated resistance (material + size), or Other (custom R/X).

NEC data

Estimated resistance

Other

Wire material

Wire size

Material of conduit

Power factor (PF)

Used for AC only

Voltage

Phase

Number of conductors

Distance (one-way)

Load current

Amps

Pass/fail threshold

Colours output based on % drop

Note: NEC table values here are a practical subset for the sizes used on this page. For specialised cable types, temperatures, or configurations, verify with your standard/manufacturer.

Wire material

Wire size

Voltage

Phase

Number of conductors

Distance (one-way)

Load current

Amps

Pass/fail threshold

Wire impedance

R (per unit length)

Reactance (AC only)

X (same unit as R)

Power factor (PF)

Used for AC only

Voltage

Phase

Number of conductors

Distance (one-way)

Load current

Amps

Pass/fail threshold

Tip: For AC, this uses effective impedance: Zeff = R·PF + X·sin(acos(PF)).

Voltage Drop Calculator

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