Engineering guides

Each guide explains how one calculation works and walks through an example taken from the calculator's tested cases. They explain the arithmetic: they are not design advice.

Voltage Drop Calculator3-Phase Voltage Drop: Formula and Worked ExampleHow the 3-phase voltage drop formula works, why it uses the square root of 3, how power factor and reactance enter, and a worked example for a 400 V cable.Gravel & Aggregate CalculatorHow Many Bags of Gravel Do I Need?How the number of gravel bags is worked out from area, depth, density and bag size, with a worked example for 20 kg, 25 kg and bulk bags.Voltage Drop CalculatorVoltage Drop Limits: What the 3% and 5% Figures MeanWhat the commonly quoted 3% and 5% voltage drop limits are, where they come from in BS 7671 and the NEC notes, and how to check a cable against them.