Capacitor Calculator

By Wojciech Sas, PhD candidate
Last updated: Jun 20, 2020

This is the capacitor calculator - an all encompassing tool that helps you answer the questions What is the capacitor code? and What is the general formula for capacitors?

While this calculator is both a code to capacity and capacity to code converter, it also finds the stored charge for a capacitor with specific parameters. Have you ever wondered what the 3-digit capacitor codes mean? In the text, you'll find an explanation - with examples!

Capacitor formula

The most general equation for capacitors states that:

C = Q / V,


  • C is the capacitance of the electronic element.
  • Q is the electrical charge stored in the capacitor.
  • V is the voltage on the capacitor.

The formula indicates that the capacitor is a passive element capable of storing electric charge as long as we apply some voltage across it.

Did you know that there are multiple types of capacitor? The most popular are parallel plates and cylindrical, but we also use spherical ones. Nevertheless, the general capacitor formula is the same in each case - charges of equal absolute values but different signs are stored on opposing sides of the capacitor.

Moreover, capacitors can be arranged both in series and in parallel. In either case, we can treat such systems as ones containing a single capacitor with a resulting capacitance being the sum of all parts.

Capacitor code

Every capacitor usually has two numbers that characterise it. These are its capacitance and the voltage rating. The latter tells us the maximum voltage at which the element will still work properly. The capacity is often written directly, so when you see a capacitor with 220 µF 25 V, it simply means that it has a capacity of 220 µF and works safely with voltages up to 25 V.

However, when the capacitance is lower than 100 µF, we can usually find a 3-digit capacitor code that defines the value. The rule is simple: The first and second digits tell us about the capacity in pF (picofarads), while the third one is a multiplier factor (the power of 10) - for the number n, the capacitance is multiplied by 10ⁿ. It's just another way to use scientific notation to describe big numbers. The last digit is usually within the range 0-6.

If there is a one- or two-digit number, it simply defines the value in pF.

Let's take a look at an example. We have a capacitor code 104:

  • The first two digits tell about the capacity in pF, which is 10 pF
  • The 3ʳᵈ digit is the multiplier factor - 10⁴ or 10,000
  • The resulting value is then 10 pF * 10⁴ = 10⁵ pF, or 100 nF, or 0.1 µF

We can also ask the reverse: What is the capacitor code for a known capacity? Let's try with a capacitor with C = 1.24 µF:

  • We need two digits for the initial two digits of the code, so it's time to round the value to two significant figures - 1.24 µF1.2 µF. So the code will start with 12·
  • To find the last digit, we have to use proper capacity units, pF - 1.2 µF = 1,200,000 pF = 12 * 10⁵ pF
  • Out of this form, we can immediately identify that the 3ʳᵈ digit is 5
  • Therefor capacitor code for a capacitance of 1.24 µF is 125

Fortunately, this capacitor calculator works as both as a code to capacity and a capacity to code converter! Just choose the appropriate field for data input, and the outcome appears in the blink of an eye!

What is capacitor tolerance code

Right next to the 3-digit capacitor code, you can usually find a letter describing the tolerance range in which the actual value of the capacitance is. Both absolute values and percentage ranges can be written. We gathered the most commonly used tolerance codes in the following table:

±0.1 pF
±0.25 pF
±0.5 pF
+80%, -20%

Let's see how our capacitor calculator deals with the code containing a tolerance letter, e.g., 104K:

  1. From the previous paragraph, we can write the value of capacity, 100 nF.
  2. Using the table above, we can work out what is the capacitor tolerance - letter K corresponds to the ±10% tolerance range
  3. The upper limit is 110% * 100 nF = 110 nF, and the lower limit is 90% * 100 nF = 90 nF
  4. The range in which we can find the actual value of capacitance is between 90 nF and 110 nF
Wojciech Sas, PhD candidate
Code to capacity converter
Tolerance code
Capacity to code converter
Tolerance capacity
Capacitor parameters
Capacitance (C)
Voltage (V)
Stored charge (Q)
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