Lighting is taken at 80%. The largest socket circuit is taken in full and the others at half. A cooker is 10 A plus 60% of the rest. Showers, heaters, EV chargers and anything marked fixed are taken at 100%.
This is a cautious screen, not a copy of the BS 7671 or On-Site Guide tables. The numbers are rounded so a pass sits inside a margin. If the result is close, or if it fails, check the current tables before you decide. Do not put this figure on a certificate in place of the published value. Real diversity allowances are often more generous, which would give a lower demand. Use this as a high-side check. Confirm the assessment method you are required to use before you order a supply or a cut-out.
These tools are quick guides for a ballpark figure. They are not certified design or test software, and a result on this page is not a design, a certificate, or a substitute for the current edition of BS 7671. Check the working and cross-reference it before you apply it to a real installation. Thanet Electrical Ltd does not accept liability for loss or cost arising from reliance on these figures, except where the law does not allow that liability to be excluded, including death or personal injury caused by negligence.
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