by Martin E. Meserve
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The equations for calculating capacitors in Series is on the left.
You might note that this is similar to resistors in Parallel.
Capacitors in Parallel are simply added together
(see the section below), whereas capacitors in Series
require a more complicated equation.
The resultant of two, or more, capacitors in Series
can be calculated using the equations on the left. With only two capacitors in
Series, the upper equation can be used to determine
the total capacitance. For three, or more, capacitors, the lower equation needs to be used.
Enter your capacitor values at the top of the diagram, under C1,
C2, and C3, and
then click outside the box to find CT for the capacitors
in Series. If you only wish to calculate the resultant value of two
capacitors, leave one of the boxes empty or enter
On the left is the equation for capacitors in parallel. The total, CT,
is the sum of all the values in parallel. The drawing to the right can be used to illustrate that
In the areas provided, enter your capacitor values for C1,
C2, and C3, and
then click outside the box, to find CT for the
capacitors in Parallel. If you only wish to calculate the resultant
value of two capacitors, leave one of the boxes empty or enter
The resultant value is always less than the
If the capacitors are of equal value, the
resultant value is equal to the value of one
of the capacitors, divided by the number of capacitors.
For example, if there are three 100 pF
capacitors in series the resultant value will be 100/3 = 33.333 pF.
If a very large capacitor and a very
small capacitor are in series, the resultant value
will only be a little bit less then the smaller
capacitor. For example, if there are a 10,000 pF
capacitor in parallel with a 100 pF capacitor the resultant
value will be 99 pF. Just 1 pF less
than the lower value resistor.
Note: There are many instances of having small capacitors in
parallel with large ones. Most commonly, this is seen in power supplies. This is done to
exploite the physical properties of the different capacitor types, rather
than adjust the value.