How this calculator works
Series resistors carry the same current. Each voltage drop is current times resistance, so the total voltage divided by current equals the sum of resistances. The missing-component calculation subtracts the known sum from the target. These are ideal positive resistances; lead and contact resistance can matter at low values.
Formula
Equivalent = sum(component values); missing = desired total - sum(known values).
Worked example
Resistors of 10, 20 and 30 ohms in series total 60 ohms. To reach 50 ohms with known resistors 10 and 20 ohms, add 20 ohms.
Advertisement
Frequently asked questions
Can I enter a list?
Yes. Separate one to ten positive component values with commas, spaces or new lines.
What if the target is too small?
No positive series component can reduce the total. Choose a larger target or change the network.
Are real component effects included?
No. Use measured values where possible and account separately for tolerances, temperature, parasitics and any magnetic coupling.