The Voltage Drop Calculator has three useful calculations:

1. Voltage Drop: Computes voltage drop of a length of cable (wire) based on length, gauge, type of wire, phase and temperature range.
2. Circular Mils and Voltage Drop: This computes voltage drop based on wire diameter in circular mils instead of wire gauge.
3. Wire Gauge Choice: Determines the lightest gauge of wire that limits the voltage drop to an acceptable level.

CLICK HERE for simple video on how to use this calculator.

The Math / Science

The Voltage Drop formula is:

V_D =  (K * P * L * C)/(A)

where:

• V_D = Voltage Drop
• K = K factor for materials
• P = Phase Constant 
• L = Length of the wire
• C = Current
• A = Cross-section area of the wire.

The type of wire  and temperature range are used to compute the K factor (Ohms - circular mils per foot).  

• K = 11 for Solid and stranded copper in the normal temperature range
• K = 12 for Solid and stranded copper in the high temperature range
• K = 18 for Solid Aluminum in the low temp range, and K = 20 for Solid Aluminum in the high temp range.
• K = 19 for Stranded Aluminum in the low temp range, and K = 20 for Stranded Aluminum in the high temp range.

The gauge is used to look up the wire cross-section area in circular mils.  Phase is used to choose a phase constant (P), where P = 2.0 for single phase and P= 1.732 for 3 phase. 

Usage

The user should measure the length of the run, and then choose the phase (single or 3), and the wire type and gauge.  Pull-down menus are given for gauge, wire type, phase and temperature range.

The voltage drop can have an adverse affect on equipment.  Typically, a 2% drop is the maximum acceptable drop in local use

Note that significantly higher volts can be used without affecting the voltage drop.  This results in a lower percentage drop in comparison.  For this reason, long lines from power stations to cities are typically in extremely high voltages and reduced for normal consumption via transformers after the distance has been run.

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Electrician Calculators

• Voltage Drop: This computes the voltage drop in volts and as a percentage over a length of cable (wire) based on length of wire, gauge, wire material, temperature range and phase.
• Wire Gauge Choice for Safe Voltage Drop: This determines the lightest gauge of wire that can be used over a run (circuit) that maintains adequate voltage.
• Circular Mils and Voltage Drop: This computes voltage drop based on wire diameter in circular mils instead of wire gauge.
• Electricity Usage Cost: This computes the cost of electricity for the use of a piece of equipment based on the power consumption rate, duration and cost of electricity.
• Electricity Consumption: This computes the amount of electricity consumed by an electrical appliance or motor over time.
• Rolling Offset: This computes the travel (T) and run (R) of a rolling offset used in conduit piping based on the offsets and angles.
• Diameter of AWG Wire: This provides the diameter of wire based on the American Wire Guide (AWG) gauge in mils and millimeters, and it also provide the cross-section area in square millimeters.
• P = V² / R: This computes power (Watts) based on the voltage (V) and resistance (R).
• DC to AC Converter: Computes the approximate voltage of Alternating Current (AC) from the voltage of Direct Current (DC).
• Diameter to Circular Mils: Computed the circular mils of a wire and the cross-section area based on the wire's diameter.