Ohmsums

Series and parallel calculator (R, C, L)

Total value of up to 8 resistors, capacitors or inductors in series and in parallel, and the two standard E12 or E24 resistors that come closest to a value you need. Results update as you type.

Indicative calculation; verify before use.

Combine up to 8 parts

Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω

Leave unused fields empty. Use a prefix: p, n, u or µ, m, k, M, G (4k7 = 4.7 kΩ, 2R2 = 2.2 Ω, 100n = 100 nF, 10u = 10 µH). m is milli, M is mega.

In series
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In parallel
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Two standard resistors for a target value

Ω

E series (IEC 60063)

WiringR1R2ResultError

Searches every pair of E12 or E24 values from 1 Ω to 10 MΩ and shows the five closest in series and the five closest in parallel. The error is against your target and ignores the parts' own tolerance (E12 parts are usually ±10 % or better, E24 ±5 % or better; check the datasheet).

How it works

Resistors: series R = R1 + R2 + … + Rn parallel 1/R = 1/R1 + 1/R2 + … + 1/Rn Inductors: series L = L1 + L2 + … + Ln (no mutual coupling) parallel 1/L = 1/L1 + 1/L2 + … + 1/Ln Capacitors: series 1/C = 1/C1 + 1/C2 + … + 1/Cn parallel C = C1 + C2 + … + Cn Two in parallel: R1 R2 / (R1 + R2) Error = (result − target) / target

In series the same current flows through every part, so resistances and inductances add up. In parallel every part has the same voltage, so conductances (1/R) add up and the total is always below the smallest part. Capacitors work the other way round: in parallel the plate areas add, so the capacitance adds; in series the total is below the smallest capacitor. Inductors are treated as ideal and magnetically uncoupled; coils that sit close together or share a core couple, and then the total is different.

The pair finder uses the E12 and E24 preferred-number series of IEC 60063 (12 and 24 values per decade: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 for E12). A pair in parallel is handy when you need a value just below a standard one; a pair in series when you need a value just above.

Worked example (resistors): 1 kΩ, 2.2 kΩ and 4.7 kΩ in series give 1 + 2.2 + 4.7 = 7.9 kΩ. In parallel 1/R = 1/1000 + 1/2200 + 1/4700 = 0.0016673 S, so R = 599.8 Ω, below the smallest resistor as it must be.

Worked example (capacitors and inductors): 100 nF and 220 nF in parallel give 320 nF; in series 100 × 220 / (100 + 220) = 68.75 nF. 10 µH and 22 µH in series give 32 µH and in parallel 6.875 µH.

Worked example (E12 pair): for 3.5 kΩ the nearest single E12 value is 3.3 kΩ (−5.71 %). 2.7 kΩ + 820 Ω in series = 3.52 kΩ (+0.57 %). 33 kΩ ∥ 3.9 kΩ = 33 000 × 3900 / 36 900 = 3.488 kΩ (−0.35 %).

Sources (checked 2026-11-03):