Calculators
Cable sizing, voltage drop, maximum demand, RCD checks, lighting layout and more. Ten calculators, each grounded in the standard it answers to, from AS/NZS 3008 cable selection with the derating factors built in to AS/NZS 3500 drainage falls. No spreadsheets, no guesswork, a result you can stand behind.
Try the calculators freeThe calculator suite
The calculations you reach for on a job, each grounded in the standard it answers to. Every one of them free with an account.
Electrical
Picks the smallest compliant cable from load, run length, install method and the derating factors, with an earth size and breaker suggestion alongside.
AS/NZS 3008.1.1Checks a cable run against the Wiring Rules voltage drop limit and suggests the smallest standard size that passes.
AS/NZS 3008Adds your connected loads and applies the Table C1 and C2 diversity factors, with a suggested main switch rating.
AS/NZS 3000Checks measured RCD trip times against the compliance limits for the circuit.
AS/NZS 3000Lighting
Sizes the total lumen output and approximate LED wattage for a room from its category, dimensions, ceiling and finish.
AS/NZS 1680Draws a top-down downlight layout for rectangle or L-shape rooms, with wall offsets and spacings in millimetres to mark out.
AS/NZS 1680Returns the downlight count and grid layout to hit a target lux level, using the lumen method.
AS/NZS 1680More trades
Works the minimum grade for a DN50 to DN100 sanitary drain run.
AS/NZS 3500.2Gives the required delivery temperature by fixture type, and whether a tempering valve is required.
AS/NZS 3500.4Calculates design wind pressure for a wall or roof from the wind region and terrain category.
AS/NZS 1170.2Grounded in the standards
A calculator is only as good as the standard behind it. Every result here is worked against the standard it answers to, with its limits built in, so the number you get is the number you can put on a compliance note.
Cable selection follows AS/NZS 3008.1.1. Current-carrying capacity is not a single tabulated figure: it is derated for the installation method, for grouping with other circuits, for ambient temperature, and for thermal insulation. Thermal insulation is the factor most often missed on site. A cable that carries a circuit comfortably in free air can fall short once it runs through a fully insulated ceiling.
Voltage drop is the second calculation, and AS/NZS 3000, the Wiring Rules, caps the total drop from the point of supply across the consumer mains, submains and final subcircuit combined. On a long run, voltage drop, not current capacity, decides the cable size. The cable you install has to satisfy both calculations: the larger answer wins.
For the full explanation of how the two calculations fit together, read the guide to cable sizing and voltage drop under AS/NZS 3008.
Why it matters
A calculation done at the quote is a calculation that saves a reorder, a callback and a hard conversation later.
Run the numbers at quoting, not after the reel is on the truck. A cable that falls short on a long run is a reorder and a return.
Every figure is worked against the standard it answers to, with its limits applied. The number you read is the number you can sign behind.
No formulas to keep current, no tabs that break when a tab is renamed. Open the calculator, enter the job, read the answer.
Every calculator is free with an account, from cable sizing to wind loading. Pro adds unlimited standards chat when you need it.
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