Capacitor Calculator

The most general equation for capacitors states that:

C = Q / V

where:

• C — Capacitance of the electronic element;
• Q — Electrical charge stored in the capacitor; and
• V — 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 capacitors? The most popular are parallel plates and cylindrical ones, but we also use spherical ones (check our spherical capacitor calculator to see how to estimate its capacitance).

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.

🔎 If you want to work out some examples of capacitive circuits, here are capacitors in series calculator and parallel capacitor calculator that may help you with the task.

Every capacitor usually has two numbers that characterize it. These are its capacitance and voltage rating. The latter tells us the maximum voltage at which the element will still work correctly. The producers often write the capacity 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 of 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 µF → 1.2 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.

• Therefore, the capacitor code for a capacitance of 1.24 µF is 125.

Fortunately, this capacitor calculator works 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!

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. We can write both absolute values and percentage ranges. We gathered the most commonly used tolerance codes in the following table:

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 determine the capacitor tolerance - the 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.