Series resistance adds up. Parallel resistance uses 1/R = 1/R1 + 1/R2 + … Branches are series strings placed in parallel with each other, which covers most ladder networks you can sketch on a pad.
Ideal resistors only. Real parts have tolerance, and this does not model temperature rise or resistor power ratings beyond the watts figure shown for the voltage you enter.
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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