AC/DC Voltage Drop Calculator
Calculate voltage drop for DC and AC electrical systems using AWG or metric cable sizes.
Voltage Drop Analysis
How It Works
The calculator estimates voltage drop across a copper conductor using the selected electrical system, source voltage, load current, cable distance and conductor size.
DC and single/two-phase AC calculations use the complete circuit path. Three-phase AC uses the standard three-phase relationship.
Important Considerations
Voltage drop depends on conductor material, temperature, installation conditions and actual operating current. Always verify the calculated value against applicable electrical codes, equipment specifications and the installation conditions.
How to interpret the estimate
Enter the source voltage, expected current, one-way cable distance and copper conductor size. Compare the estimated final voltage with the equipment’s documented input range. For example, a 1 V drop from a 12 V source leaves 11 V; the same drop from 24 V leaves 23 V.
This is a planning estimate, not a cable-sizing or electrical-code compliance check. The form has no inputs for power factor, cable reactance, conductor temperature or installation method, so it cannot model all AC conditions. It also does not verify ampacity, protective devices or PoE negotiation.
Physical Security & Access Control
Estimate the voltage available to a remote DC device. Check its startup current and minimum operating voltage separately.
Data Center Infrastructure
Use the result as an initial comparison of cable lengths and conductor sizes. Validate the actual installation and equipment requirements before making design decisions.
PoE & Network Routing
PoE requires additional checks for the power source, powered device, cable category and pair resistance. This calculator does not certify a PoE link.
Frequently Asked Questions
What is an acceptable voltage drop percentage?
There is no single percentage that this tool can certify for every installation. Compare the result with the applicable local requirements and the equipment manufacturer’s input-voltage limits.
Why does wire gauge matter in DC circuits?
Direct Current (DC) circuits often operate at lower voltages (like 12V or 24V). A 2 V drop is 16.7% of 12 V but approximately 0.9% of 220 V; whether it is acceptable depends on the connected equipment. Therefore, choosing the correct copper cross-section (mm²) is vital to minimize resistance.
Should I calculate the distance one-way or round-trip?
This calculator is designed to factor in the total circuit path. You simply need to input the one-way distance from the power source to the equipment, and the underlying algorithm automatically accounts for the return path of the current.
Worked comparison: a remote DC load
With DC selected, enter 12 V, 2 A, 50 m one-way and 0.5 mm² copper. The calculator returns approximately 6.88 V of drop, leaving 5.12 V at the load. At 2.5 mm² with the other inputs unchanged, the drop falls to about 1.38 V and the final voltage rises to 10.62 V.
This comparison demonstrates the effect of conductor area in the model. It does not establish that either cable is suitable. Compare the remaining voltage with the device’s specified operating range and assess current-carrying capacity and protection separately.
Choose the correct distance and units
Enter the physical one-way cable run in meters; do not double it before entering a DC or two-conductor circuit. The calculation includes the return path. Select either metric area or AWG and check the conductor displayed in the result before using the output.
Check the load assumptions
The model treats the entered current as fixed. Constant-power electronics may draw more current as voltage falls, and startup current may differ from normal operation. Temperature also changes copper resistance. For AC, power factor and reactance are not inputs, so use the estimate only where its simplified assumptions are appropriate.
For three-phase work, confirm that your voltage and current definitions match a balanced three-phase calculation. The generic two-phase label does not model every two-phase or split-phase wiring arrangement; use a calculation specific to the actual circuit when that distinction matters.