Please read before using the Voltage Drop Calculator
Last updated: April 2026
⚡ This calculator is provided as a free reference guide only. It does not constitute professional electrical, engineering or design advice. All electrical installation work must be carried out by a licensed electrician in accordance with applicable electrical standards and local regulations.
The voltage drop calculator and tools provided on this website (voltagedrop.com.au) — including the Single Phase AC, Three Phase AC, DC, Series Runs and Motor Starting calculators — are intended as general guidance tools to assist with preliminary planning and estimation only.
While every effort has been made to ensure the accuracy of the formulas, reference data and cable tables presented, we make no warranty, express or implied, as to the accuracy, completeness, reliability or suitability of any information produced by these tools for any particular purpose.
Results produced by these calculators are mathematical estimates based on the inputs you provide and standard industry assumptions. Actual real-world performance will vary depending on factors including but not limited to: cable temperature, derating factors, installation conditions, ambient temperature, harmonic distortion, power factor variation, contact resistance, and variations between manufacturers.
To the fullest extent permitted by law, we exclude all liability for:
These tools are provided "as is" and "as available" without any guarantee of fitness for a particular purpose.
In Australia, all electrical installation work — including cable sizing, circuit design, switchboard work, and connection of any fixed electrical equipment — must be carried out by a licensed electrician in accordance with:
The voltage drop, cable sizing, ampacity and motor starting calculations provided by this tool are for planning and estimation purposes. They do not replace a formal electrical design, site inspection, load flow analysis or compliance assessment by a qualified electrical engineer or licensed electrician.
The ampacity (current-carrying capacity) values shown in this calculator are indicative figures based on typical installation conditions for copper conductors in conduit at standard ambient temperature. Actual cable ratings depend on:
Always refer to AS/NZS 3008.1 or the cable manufacturer's published derating tables for the correct current-carrying capacity for your specific installation conditions. The ampacity values in this tool should not be used as the sole basis for cable selection.
The motor starting voltage drop calculations provided are indicative estimates based on typical direct-on-line (DOL) inrush current multiples and assumed starting power factors. Actual motor starting performance depends on motor design, connected load, starting method, supply impedance, and the characteristics of the motor controller. Always obtain starting current and power factor data from the motor manufacturer's documentation for critical installations.
This website generates search links to products on Amazon Australia, Amazon.com, Amazon India and Takealot as a convenience to users. We participate in the Amazon Associates affiliate program, which means we may earn a small commission if you purchase a product through one of our links, at no additional cost to you.
Product links are generated automatically based on your calculator inputs and are not endorsements of any specific product or brand. We have not tested, verified or taken responsibility for the quality, safety, compliance or suitability of any product found through these links. Always verify that any cable or electrical product you purchase meets the applicable Australian or regional standards and is appropriate for your specific application.
Use of this calculator does not create any professional, contractual or advisory relationship between you and us. The information provided is general in nature and does not take into account your specific circumstances, site conditions, supply authority requirements or project requirements.
If you are unsure about any aspect of your electrical installation, we strongly encourage you to consult a licensed electrician before proceeding.
This calculator includes regional modes for Australia, United States, India and South Africa. However, core formulas, default cable sizes, default voltage drop limits and some reference data reflect Australian practice under AS/NZS 3000. International users are solely responsible for verifying that any calculations produced comply with their local electrical codes, standards and supply authority requirements before use.
In particular: voltage drop limits, cable rating methods, permitted conductor materials, circuit protection requirements and licensing rules vary significantly between jurisdictions. The regional toggle adjusts certain defaults but does not constitute a full compliance assessment under any national standard.
The content, layout, code and tools on this website are our intellectual property. You may use the calculator freely for personal and commercial planning purposes, but you may not reproduce, redistribute or republish the tools or their underlying code without written permission.
We reserve the right to update or amend this disclaimer at any time without notice. Continued use of the tools following any changes constitutes your acceptance of the updated terms.
These terms are governed by the laws of the state of Victoria, Australia. By using this website, users in all jurisdictions agree that any disputes arising from the use of this website shall be subject to the exclusive jurisdiction of the Australian courts, to the fullest extent permitted by applicable law.
If you notice an error in any of our calculations or have a suggestion to improve the tool, please reach out via lighttools.com.au. We are always happy to improve the accuracy and usefulness of these free tools.