How this calculator works
Parallel resistors share voltage. The branch conductances add, giving an equivalent resistance lower than every branch. The missing-component mode subtracts the known conductance from the target conductance before taking its reciprocal.
Formula
1/Xeq = sum(1/Xi); Xmissing = 1/[1/Xtarget - sum(1/Xknown)].
Worked example
A 10 ohm resistor in parallel with 20 ohms gives 6.666667 ohms. Adding 10 ohms in parallel with another 10 ohms gives 5 ohms.
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Frequently asked questions
What does the component count mean?
It counts known components. Missing-component mode adds one more, so a single known component is allowed.
Why is a requested total rejected?
A passive positive component must change the total in the direction allowed by the connection. Equality would require a zero or infinite ideal component.
Are real component tolerances included?
No. Enter measured values or calculate tolerance extremes separately. Ratings and parasitic effects require a separate check.