Example 1
Cz = 0.5 µF.
Series capacitance calculator
Type C1 [F] and C2 [F]. The calculator computes 1/Cz = 1/C1 + 1/C2: two 1 µF capacitors are 0.5 µF, and 1 µF and 2 µF is about 0.667 µF. In series Cz is smaller than each branch.
Parallel: Cz = C1+C2. One C: C = Q/U.
Result
Capacitance C₁ (F) and Capacitance C₂ (F). The result shows up here.
How it works
Series equivalent capacitance obeys 1/Cz = 1/C1 + 1/C2. At 1 µF and 1 µF you get 0.5 µF. At 1 µF and 2 µF: Cz = 2/3 µF ≈ 0.667 µF. At 10 µF and 10 µF you get 5 µF. In series Cz drops, the opposite of resistors, because the charge is the same and voltages add, so C = Q/U falls.
The form has two fields: C1 and C2 in farads. Type 1 µF as 1e-6, not as 1. The result is in F. A comma, a period, and 1e-6 mean the same C.
Both C values must be positive. Zero does not divide. Both fields need a number before 0.5 µF appears. In series the charge on both is the same, and U1 + U2 = Uz.
Parallel Cz = C1 + C2 and grows. Here the reciprocals add. C = Q/U is one capacitor. Energy E = ½ C U² already takes one C, for example this Cz.
A very large C2 barely changes Cz: 1 µF and 100 µF give about 0.99 µF, close to the smaller one. Three capacitors take two steps: a pair, then that Cz with the third.
Type 1e-6 and 1e-6, click Calculate, and check 0.5 µF. Then 1e-6 and 2e-6: about 0.667 µF. The calculator adds reciprocals; it does not guess a breakdown voltage.
How to use
- In the first field enter C1 in farads, for example 1e-6 (1 µF). 1 µF is 1e-6, not 1.
- In the second field enter C2 in farads, for example 1e-6 or 2e-6.
- Click Calculate. Two 1 µF give 0.5 µF, because 1/Cz = 1/C1 + 1/C2. 1 µF and 2 µF give about 0.667 µF.
- Zero in C1 or C2 is rejected. Both fields need a positive number.
- For the sum C1+C2, open parallel capacitance. One C is on C = Q/U.
Formula
1/Cz = 1/C1 + 1/C2
C1, C2 > 0.
Cz, C1, and C2 in series
Series capacitances: 1/Cz = 1/C1+1/C2. Two 1 µF capacitors give 0.5 µF. 1 µF and 2 µF give about 0.667 µF. Cz is smaller than each one.
- Cz
- Series equivalent [F]. Always below the smaller of C1 and C2.
- C1
- First capacitor [F]. Type 1 µF as 1e-6, not as 1.
- C2
- Second capacitor [F]. Equal to C1 gives Cz = C1/2.
Real-life examples
Example 2
Cz ~ 0.667 µF.
Example 3
Cz = 5 µF.
Example 4
Cz ~ 66.7 nF.
Example 5
1 µF + 100 µF -> Cz ~ 0.99 µF.
Example 6
Typical catalogue values.
Example 7
Cz = 1.2 µF.
Example 8
10 nF + 10 nF -> 5 nF.
Example 9
C<sub>1</sub> = 4.7 µF, C<sub>2</sub> = 2.2 µF.
Ways to use this calculator
- You put two 1 µF in series to 0.5 µF.
- You check 1 µF and 2 µF: about 0.667 µF.
Frequently asked questions
How much Cz with two 1 µF in series?
Equivalent capacitance is 0.5 µF. Two equal capacitors in series give half of one, not the sum you get in parallel.
How much at 1 µF and 2 µF?
You get about 0.667 µF, which is 2/3 µF. Product over sum, after you type farads.
Which units do I type?
Both capacitances C1 [F] and C2 [F]. Result Cz [F]. Type 1 µF as 1e-6, not as 1.
How is this different from parallel?
Series uses reciprocals and Cz is smaller than each branch. Parallel uses Cz = C1 + C2 and the result grows.
Why does series C drop while series R grows?
In series the plates sit one after another, so total capacitance falls. Series resistors add ohms, because current has one path.
Does a comma in 0.000001 work?
Yes. 0.000001, 0,000001 and 1e-6 are the same C [F]. 1e-6 is easier.
Where is C = Q/U?
On the capacitance-from-charge page. Here you already combine two C values; you do not solve one C from Q.
Where is energy?
On the capacitor-energy page. There E = ½ C U². Here only two capacitances in series.
What about C = 0?
Zero farads in series blocks the chain. The calculator cannot form a clean Cz then, because you divide by C.
How much at 10 µF and 10 µF?
You get 5 µF. Two equals in series always give half of one.
Knowledge sources
The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.
Page updated in 2026.