About the Capacitor Calculator
This capacitor calculator combines up to four capacitors in series or in parallel, then shows the charge they hold and the energy they store at a given voltage. It also decodes the three-digit EIA markings printed on ceramic and film capacitors — for example 104 means 100,000 pF, or 100 nF — including tolerance letters such as J and K.
Use it when you need a value you do not have in the parts drawer, when checking how voltage splits across capacitors stacked in series, or when estimating the energy in a bulk or supercapacitor bank. Enter capacitances in microfarads and leave unused slots at zero.
The results assume ideal capacitors. In a real series string, leakage current and tolerance make the voltage share unevenly, so high-voltage banks use balancing resistors, and each capacitor’s voltage rating should comfortably exceed the voltage shown for it.
With the default inputs, the total capacitance is 6.875 µF. Change any value above to recalculate instantly.
How to use the capacitor calculator
- 1Choose whether the capacitors are wired in series or in parallel.
- 2Enter each capacitance in microfarads; leave unused slots at 0.
- 3Enter the voltage applied across the combination.
- 4Read the total capacitance, charge, stored energy and per-capacitor voltages.
- 5Type a printed code such as 104 or 472J to decode it.
Formula and method
Capacitors in parallel share the same voltage, so their plate areas effectively add and capacitances sum. In series they carry the same charge, so the reciprocals add and the total is always smaller than the smallest capacitor. The voltage across each series capacitor is Q ÷ Ci, which is why the smallest one sees the largest share.
Charge is Q = C·V (µF × V = µC) and stored energy is E = ½·C·V² (reported in millijoules). For three-digit codes the first two digits are significant figures and the third is the number of zeros to add, with the result in picofarads; a multiplier of 8 or 9 means ×0.01 or ×0.1, and an R marks the decimal point (4R7 = 4.7 pF).
- C
- Capacitance (µF)
- Q
- Charge (µC)
- V
- Voltage across the capacitor(s)
- E
- Stored energy
- ab, c
- Significant digits and multiplier digit of a 3-digit code
Worked examples
10 µF and 22 µF in series at 12 V
1 ÷ (1/10 + 1/22) = 6.875 µF. At 12 V the charge is 6.875 × 12 = 82.5 µC and energy is ½ × 6.875 µF × 12² = 0.495 mJ. The 10 µF part carries 8.25 V and the 22 µF part 3.75 V. The default code 104 decodes to 100,000 pF (100 nF).
Three capacitors in parallel at 50 V
Parallel values add: 100 + 47 + 4.7 = 151.7 µF, holding 7,585 µC and ½ × 151.7 µF × 50² ≈ 189.6 mJ. The marking 472J is 47 × 10² = 4,700 pF (4.7 nF) with ±5% tolerance.
Two 2.7 V supercapacitors in series
Two 1 F (1,000,000 µF) cells in series make 0.5 F, rated for 5.4 V. They store ½ × 0.5 × 5.4² = 7.29 J (7,290 mJ). 4R7 marks a 4.7 pF capacitor.
Frequently asked questions
How do you calculate capacitors in series?+
Add the reciprocals and invert: 1/C = 1/C1 + 1/C2 + …. For two capacitors this simplifies to C1·C2 ÷ (C1 + C2). The result is always smaller than the smallest capacitor.
What does 104 mean on a capacitor?+
It is 10 followed by four zeros in picofarads: 100,000 pF, which is 100 nF or 0.1 µF. Likewise 103 is 10 nF, 472 is 4.7 nF and 101 is 100 pF.
How much energy does a capacitor store?+
E = ½·C·V² joules with C in farads. A 1,000 µF capacitor charged to 50 V stores ½ × 0.001 × 2,500 = 1.25 J, and energy rises with the square of voltage.
Why put capacitors in series?+
To reach a higher voltage rating than one part allows, as with supercapacitor stacks, or to make an odd capacitance value. Balancing resistors are often added so leakage differences do not overstress one capacitor.
What do the letters J, K and M mean on a capacitor?+
They are tolerance codes: J is ±5%, K is ±10% and M is ±20%. F and G mean ±1% and ±2%, and B, C and D give absolute tolerances for small picofarad values.