Electrical Calculators
NZ-focused planning calculators for licensed electrical workers and inspectors. Free, no login required.
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Mains Cable Selection
Find the smallest compliant mains cable for your load and run.
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Voltage Drop
Check volt drop against the 5% limit for any cable run.
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Earth Fault Loop Impedance
Check measured Zs against the maximum allowed for your breaker.
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Ohm's Law
V, A, Ω, W — enter any two, get the other two instantly.
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Three-Phase Converter
Convert kW, kVA and amps between single and three phase.
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Maximum Demand
Work out maximum demand for a house or small commercial job.
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Solar String Sizing
Work out min and max panels per string for your inverter.
For guidance only. These calculators are planning aids for licensed electrical workers and inspectors. All results must be independently verified against the current editions of AS/NZS 3000:2018, AS/NZS 3008.1.2, and other applicable standards before being relied on for any installation. CertMate accepts no responsibility or liability for any work carried out, decisions made, or certification issued in reliance on these results. The certifying electrical worker remains solely responsible for compliance with the Electricity (Safety) Regulations 2010 and all applicable New Zealand law.