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Electrical calculators & unit converters

170+ free tools for engineers, electricians and DIYers. Every result comes with the formula, a worked example and a reference table.

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Wiring & earthing guides

IEC 60364 and BS 7671 terms explained in plain language, with diagrams.

SPD Installation: Connection Types, Lead Length and Back-up Protection A surge protective device is only as good as the way it is connected. The same Type 2 SPD that clamps a… 6 min read Step Voltage: Definition, Calculation and Safe Limits Step voltage is the voltage between two points on the surface of the ground one metre apart. The metre is not arbitrary:… 5 min read 1P, 1P+N, 2P, 3P and 4P Circuit Breakers: How Many Poles You Need A pole is one set of contacts inside a circuit-breaker, switching one conductor. A single-pole breaker interrupts one conductor, a double-pole breaker… 5 min read MCB Trip Curves B, C and D: How to Read Them and Which to Use The letter in front of the rating on a miniature circuit-breaker, the B in B16 or the C in C32, tells you… 6 min read Shunt Trip and Undervoltage Release: Circuit-Breaker Accessories Explained A circuit-breaker on its own reacts to only two things: overload and short circuit. Everything else that should make it open, such… 6 min read AFDD (Arc Fault Detection Device): How It Works and Where It Is Required An arc fault detection device (AFDD) is a protective device that watches the current waveform of a final circuit and disconnects it… 7 min read

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Each calculator states the formula it applies and shows a worked example, so you never have to trust a number blindly. The guides quote the IEC 60364 and BS 7671 clauses they rely on.

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