By the VoltageDropCalculator team
VoltageDropCalculator.net is our own site: a free, browser-based voltage drop calculator. This post explains one number it shows that people often skip past: the voltage at the load.
When you run a calculation, you enter the load in amps, watts or horsepower, pick a system voltage (12V, 24V or 48V DC, or 120, 208, 240, 277 or 480V AC, single or three phase), choose copper or aluminum and PVC or steel conduit, and enter the one-way run length. The result shows three things: the voltage drop, the voltage at the load, and a suggested conductor size.
The voltage drop tells you how many volts are lost in the wire. The voltage at the load is what is left when the current reaches the equipment: the supply voltage minus that drop. It is the number the equipment actually sees, so it is often the easier one to reason about. A motor, a charger or an LED driver cares about the voltage at its terminals, not about the loss along the way.
Reading the two together helps. The same drop in volts is a much bigger share of a 12V DC battery circuit than of a 240V AC circuit, so on low-voltage systems the end voltage can fall below what the device needs even when the drop looks small.
The calculator also compares the result with the NEC recommendation of 3% for a branch circuit and 5% total, using NEC Chapter 9 Table 8 resistance values, and suggests a conductor size. If the end voltage is too low, try a larger wire size, a shorter run or parallel sets and see how the voltage at the load changes.
Try it at https://voltagedropcalculator.net/ or browse the preset 12V–480V calculators at https://voltagedropcalculator.net/calculators/. Results are for reference only; verify against the code adopted where you work.