Voltage Drop Calculator

Voltage Drop Calculator

Wire / cable voltage drop calculator is available here for free, learn how to calculate.

  1. Voltage drop calculator
  2. Voltage drop calculation

Voltage Drop Calculator

Calculates Voltage Drop at 20 degree Celsius.

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Voltage drop calculations

DC / single phase calculation

Let’s Take the voltage drop V measured in volts (V) is totally equal to the wire current I measured in amps (A) times 2 times one way of the wire length L in feet (ft) times the resistance of the wire per 1000 feet R measured in ohms (Ω/kft) and divided by 1000:

Vdrop (V) = Iwire (A) × Rwire(Ω)

= Iwire (A) × (2 × L(ft) × Rwire(Ω/kft) / 1000(ft/kft)

The voltage drop V is equal to the wire current I in amps (A) multiplied twice the wire length L measured in meters (m) and further multiplied the wire resistance per 1000 meters R measured in ohms (Ω/km) and divided by 1000:

Vdrop (V) = Iwire (A) × Rwire(Ω)

= Iwire (A) × (2 × L(m) × Rwire (Ω/km) / 1000(m/km)

3 phase calculation

The voltage drop V in volts (V) is totally equal to the square root of the 3 times of the wire current I measured in amps (A) times the 1 way wire length L measured in feet (ft) times the resistance of wire per 1000 feet R measured in ohms (Ω/kft) and divided by 1000:

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(ft) × Rwire (Ω/kft) / 1000(ft/kft))

The voltage drop V in volts (V) can be calculated as the square root of 3 times the wire current I which is measured in amps (A) times one way of the wire length L in meters (m) times the resistance of wire per 1000 meters R measured in ohms (Ω/km) and divided by 1000:

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(m) × Rwire (Ω/km) / 1000(m/km))

Wire diameter calculations

Assume n number of gauge wire diameter dn in inches (in) is totally equal to 0.005 in times the 92 raised to the power of number 36 minus gauge number n, and finally divided by 39:

dn (in) = 0.005 in × 92(36-n)/39

The number n gauge wire diameter dn in millimeters (mm) is totally equal to the 0.127 mm times the 92 raised to the power of 36 minus the gauge number n, and divided by 39:

dn (mm) = 0.127 mm × 92(36-n)/39

Wire cross sectional area calculations

Let’s take n gauge wire with cross sectional area An measured in kilo-circular mils (kcmil) is totally equal to 1000 times the square wire diameter d measured in inches (in):

An (kcmil) = 1000×dn2 = 0.025 in2 × 92(36-n)/19.5

The number n gauge wire with cross sectional area An is measured in square inches (in2) is actually equal to pi divided by the 4 times of the square wire with diameter d measured in inches (in):

An (in2) = (π/4)×dn2 = 0.000019635 in2 × 92(36-n)/19.5

The n gauge wire’s cross sectional area An in square millimeters (mm2) is equal to pi divided by 4 times the square wire diameter d in millimeters (mm):

An (mm2) = (π/4)×dn2 = 0.012668 mm2 × 92(36-n)/19.5

Wire resistance calculations

Assume n gauge wire with resistance R which is measured in ohms per kilofeet (Ω/kft) is totally equal to the 0.3048×1000000000 times the resistivity of the wire ρ in ohm-meters (Ω·m) and further divided by 25.42 times the cross sectional area An which is measured in square inches (in2):

Rn (Ω/kft) = 0.3048 × 109 × ρ(Ω·m) / (25.42 × An (in2))

The n gauge resistance of the wire R in ohms per kilometer (Ω/km) is totally equal to 1000000000 times the resistivity of wire ρ which is measured in ohm-meters (Ω·m) divided by the cross sectional area An in square millimeters (mm2):

Rn (Ω/km) = 109 × ρ(Ω·m) / An (mm2)

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