Considering Smythy as a free JCalc alternative
Looking for a free tool for a cable run or demand check? Smythy covers the calculations below, with the method and assumptions shown beside the result. This guide explains where those tools fit and which tasks need a broader design tool or assessment.
What Smythy covers
| Calculator | Method |
|---|---|
| Cable sizing | Copper V-75 multicore: AS/NZS 3008.1.1:2025 Tables 3.15 and 3.18 with correction factors, Table C8 voltage drop, optional short-circuit check |
| Voltage drop | AS/NZS 3000:2018 Appendix C Table C8 simplified method |
| Maximum demand | AS/NZS 3000:2018 Appendix C Tables C1 (column 2), C2 and C3, assessed phase by phase |
| Earth fault loop | Table 8.1 maximum Zs and the Paragraph B5.2 route length check |
| Conduit fill | Paragraph C6.2 space factors with indicative or manufacturer dimensions |
| All calculators | Motor current, kW/kVA, earth conductor size, DC tools and engineering screening tools |
All calculators are free without an account. Results can be printed or downloaded as a watermarked PDF that includes the working.
What it does not do
- Cable sizing for aluminium or XLPE (X-90) cable, single-core cables or cables in parallel.
- A complete cable design using site-specific impedance data. The voltage-drop and cable sizing tools use the simplified Table C8 method; the separate multi-segment voltage-change tool uses representative impedance values.
- Full protective-device selection or discrimination studies. Protection coordination tools screen entered timing margins; they do not establish full selectivity.
- Shared project files, cable schedules or account storage. Keep a PDF when you need a separate record of the calculation.
- Certifying an installation. You remain responsible for the design and the certificate.
When you need more than a calculation
For cable types or arrangements outside this model, choose a design tool with the required data and methods. If you need shared project files, cable schedules or formal design reports, check those requirements before choosing software. A product name or price alone does not establish that it covers your installation.
For a supported calculation, open the matching Smythy tool from the table above. Enter the installation details, review the working and check the result against the applicable standards and equipment data.