 # Voltage Drop Calculator

## For Direct Current (DC) Power Systems    Oops! Something went wrong while submitting the form.

## How It Works

Our voltage drop calculator estimates the power loss and voltage drop along cables carrying direct current (DC) power. This is a great tool to obtain an estimation of how much power you need to provide to ensure remote DC loads have sufficient voltage.

In AC (alternating current) power systems and, to a much lesser extent, in DC power systems, it's necessary to generate more power than will be consumed by devices. This is because a certain amount of power will be lost along cables due to various types of line losses, such as resistance. If you'd like to learn more about the types of line losses, you can read about them on our blog: The 3 Types of Line Losses Along Transmission Lines.

Here's how this calculator works. A number of factors influence how much power loss and voltage drop occur along cables, including:

Cable gauge size (AWG and/or mm²), cable length, type of power (AC or DC), as well as voltage and current at the power source.
First, this calculator determines resistance along cables based on the cable gauge and length. Then it takes available power at the source into account before providing the total estimation of power loss and voltage drop along cables. The formulas integrated into this calculation include estimations on power lost due to the types of line losses that are known to impact voltage drop in DC power systems.

## Back to Calculator Home ## Formulas for Voltage Drop and Power Loss Along Cables

These formulas are used to calculate the resistance of the cable (ohms)

Calculate the diameter in millimeters (d_mm) of the wire using the American Wire Gauge (AWG).

d_mm 0.127 92^ (

36 - AWG

39

)

Convert the diameter to meters (d_m).

d_m d_mm

1000

Calculate the cross-sectional area (A) in square meters (A = d_m²).

A_m² π (

d_m

2

The cross sectional area of the wire can also be given in mm² using the following formula.

A_mm² π (

d_mm

2

Resistivity (p)

It’s necessary to use the resistivity in order to calculate resistance. Resistivity is a measure of a material's property to oppose the flow of electric current, and is expressed in Ohm-meters (Ω⋅m). This calculator assumes the material of the wire is copper, so we use the following constant:

p 1.72 10⁻⁸ Ω⋅m

Resistance per Meter @ 25 Degree Celsius (ohm/m)

The longer and thinner the wire, the higher the resistance in the wire. The shorter and thicker the wire, the lower the resistance in the wire. This can be expressed in the below formula.

ohms/m p

A_m²

Total Resistance (ohms)

ohms ohms/m cable run length

Total Power At Source

Power equals voltage multiplied by current.

W_source V_source I

Total Voltage Drop (V_drop) Formula

Voltage drop is energy wasted along cables in the form of heat, and it's used to calculate voltage at the load. To get total voltage drop, it's necessary to multiply resistance (total ohms) by 2. This is because the power isn't only travelling from the source to the load, but also from the load to the source (it has to complete the entire circuit).

V_drop I (ohms * 2) V_source V_drop

Power equals voltage multiplied by current.  I

Power Loss (W_loss)

W_loss W_source 