Free Electrician Calculators
Cable sizing, voltage drop, conduit fill, and more — built for Australian sparkies and based on AS/NZS 3000 & AS/NZS 3008.
Cable Sizing AS3008
Pick the right cable size using AS/NZS 3008 derating tables.
Voltage Drop Calculator
Check single & three-phase volt drop against the 5% limit.
Conduit Fill Calculator
Verify cable count stays within the 40% space factor.
Maximum Demand Calculator
AS/NZS 3000 Table C1 demand calc for dwellings.
Watts ⇆ Amps Converter
Convert watts to amps or amps to watts at any voltage.
Ohm's Law Calculator
Solve V, I, R, or P when you know any two.
kW to Amps Calculator
Single & three-phase kW to amps conversion.
Earth Electrode Resistance
Estimate ground rod resistance from soil type.
Circuit Breaker Sizing
Match MCB/RCBO ratings to cable capacity.
RCD Testing Compliance
Validate safety switch trip times against AS/NZS 3760.
Solar DC Cable Sizing
Size PV array cables to AS/NZS 5033 limits.
Transformer Sizing
Calculate required kVA for step-down transformers.
Power Factor Correction
Size capacitor banks to improve facility power factor.
Cable Length Calculator
Max cable run length or estimate drum stock.
Fault Loop Impedance
Check Zs limits for breaker disconnection times.
Every electrical installation in Australia is governed by AS/NZS 3000 (the Wiring Rules) and AS/NZS 3008.1.1 (cable selection). These calculators are built to help licensed sparkies, apprentices, and electrical engineers run quick compliance checks without flipping through physical standards books.
Why do electricians need specialised calculators?
Most generic online calculators use American wire gauges (AWG) and 120V/60Hz assumptions. That is useless in Australia where we run 230V/50Hz single phase and 400V three phase, measure cables in mm², and must comply with a completely different set of installation standards.
A cable that passes NEC rules in the US might fail AS/NZS 3008 derating requirements in Australia because of different ambient temperature assumptions, installation methods, or grouping corrections.
These tools are calibrated for Australian conditions. They use the correct voltage references, the correct conductor resistance values from AS/NZS 3008 tables, and the correct space factor limits from AS/NZS 3000 Appendix C.
How do these tools fit into a typical wiring job?
On a standard domestic rewire or new build, a sparky typically works through the following technical steps:
- Estimate the load — use the Maximum Demand Calculator with AS/NZS 3000 Table C1 diversity factors to size the main switch and sub-mains.
- Select the cable — use the Cable Sizing Calculator to find the minimum cable size that carries the required current under your specific installation method.
- Verify voltage drop — plug the cable size and route length into the Voltage Drop Calculator. If it exceeds 5% end-to-end, step up to the next cable size.
- Check conduit capacity — if pulling cables through conduit, use the Conduit Fill Calculator to make sure you are within the 40% fill limit.
- Size protection — use the Circuit Breaker Sizing tool to match MCB ratings to cable capacity and load current.
- Test and certify — after installation, use the Fault Loop Impedance and RCD Testing calculators to verify the installation meets disconnection time requirements.
Every step references a different part of the Australian Standards. These tools let you cross-check your manual calcs quickly without carrying a full set of standards books to site.
Who are these tools built for?
- Licensed electricians running their own contracting business
- Electrical apprentices studying for their capstone or licence exams
- Electrical engineers doing preliminary design calcs before detailed engineering
- Solar installers checking DC cable compliance under AS/NZS 5033
- Building inspectors verifying contractor submissions
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