Electrical Load Calculator
Add appliances to calculate total electrical load in watts and amps. Get recommended cable sizes and MCB ratings with diversity applied — all based on UK 230V standards.
Frequently asked questions
How do I calculate electrical load for a circuit?
Add up the wattage of all appliances on the circuit, then divide by the voltage (230V in the UK) to get the current in amps. Apply a diversity factor — typically 100% for the largest appliance and 40% for the rest — to get the design current.
What is diversity in electrical calculations?
Diversity is the principle that not all appliances on a circuit will run at full load simultaneously. BS 7671 provides diversity factors for different installation types. For domestic circuits, the first appliance is rated at 100% and additional appliances at 40%.
How do I choose the right cable size?
Select a cable whose current-carrying capacity exceeds the design current after applying correction factors for ambient temperature, grouping, and thermal insulation. Common sizes: 1.0mm² for lighting (up to 16A), 2.5mm² for sockets (up to 20A), 4mm² for cookers (up to 32A), and 6mm² for showers (up to 45A).
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