Introduction

This page contains two calculators. One for creating a Precision Capacitor, and the other for creating a Custom Capacitor.

The Precision Capacitor uses only two capacitors and is useful when you need a very specific capacitor, say for a active filter. Because its a low voltage circuit, your not really worried about the voltage, but the value you are looking for is not a standard capacitor value. You might be able to find it in a 1% capacitor. But do you really need to go to that expense when two common capacitors will get you just as close to the target value?

A Custom Capacitor uses two to ten capacitors, of the same value. It can server two purposes. Like the Precision Capacitor, you might need a non-standard capacitor value. Or, you might need a higher voltage capacitor than is readily available. The correct combination of capacitor could provide you with the value you need and the correct voltage.

Precision Capacitors

This calculator determines the value of two standard value capacitors (C_A and C_B) which, when connected in parallel, will result in a net capacitance C_T that will be within very close tolerances, of almost any value you want.

The program works by first selecting a standard capacitor (C_A) that is close, but larger, than the specified capacitance. It then determines the value of another standard capacitor (C_B) that can be placed in parallel with the first one (C_A) to obtain the capacitance required. Because we are using standard capacitors, the final value will not be exact, but it should be within 2 or 3 percent.

Just enter the Target Capacitance value, at the top of the calculator.

Note: You can enter a value that is a standard capacitor value. In that case the calculator will find the next highest standard capacitor value for C_A. It will then calculate an appropriate value for C_B to meet your target requirement. However, it may come up with a unwieldy, unrealistic, solution. But it will let you know you entered a standard capacitor value.

Custom Capacitors

The calculator on the right will list Standard Value Capacitors (SVC) capacitor combinations that will be very close to almost any reasonable value that you require. The combinations will be made from "N" standard common SVC capacitors, connected in series and in parallel. Where "N" can be from 1 to 5.

For example: Say you need a 1,234 pF capacitor, but don't have anything available that is close enough. You could use a 1,200 pF capacitor or a 1,300 pF capacitor, which would be within 2.8% and 5.3%, respectively. But if you need a value that is closer, entering "1234" in the space available would show you that 5 - 6,200 pF capacitors in series, or 2 - 620 pF capacitors in parallel would be within 0.5% of 1,234 pF. Six capaitors may be a little clumsy, but two wouldn't be too bad.

Other combinations exist that may suit your needs better. I only included a grouping of ten combinations for series and parallel connection.

The calculator takes the Target Capacitance and calculates an array of capacitors values that are 1, 2, 3, ... 5 times the Target Capacitance. It then finds the closest SVC capacitors above (≥), and below (≤), these values. The closest SVC capacitor values are then divided by their multiplier (1, 2, 3, ... 10) and matched to the Target Capacitance.

The table shows the percentage it is different from the Target Capacitance. There are two sides to the table. The listings on the left uses capacitor multiples that are less than, or equal. The listing on the right uses capacitor multiples that are greater than, or equal. Combinations within 5% of the target value are high-lighted in BLUE.

Just enter the value of the custom capacitor you want and click outside the box.