Capacitor Code Calculator

Small capacitors are too tiny to print a full value on, so manufacturers stamp them with a short code instead, and this calculator decodes that code into a capacitance you can actually use, shown in picofarads, nanofarads and microfarads at once. The most common marking is a three-digit code such as 104 or 223. It works just like the resistor colour code: the first two digits are the significant figures and the third digit tells you how many zeros to add, giving the value in picofarads. So 104 is 10 followed by four zeros, which is 100,000 pF, or 100 nF, or 0.1 uF, the same part written three different ways. Smaller capacitors often just print the value directly, so a code of 22 simply means 22 pF, and many parts add a tolerance letter such as J, K or M after the number, telling you how far the real value may stray from the nominal one. Enter the code, choose a tolerance letter if there is one, and the calculator returns the capacitance in all three units along with the tolerance, taking the guesswork and mental arithmetic out of reading a part. That is genuinely useful when you are sorting a parts drawer, following a circuit diagram, repairing electronics, or building a project from a kit, where matching the right capacitor matters and the codes are easy to misread. It is also a handy learning aid for electronics and physics students getting to grips with component markings and the picofarad, nanofarad and microfarad scale. The code system and a worked example are explained clearly below, so you can soon read most capacitors at a glance.

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100 nF
capacitance
Picofarads100,000 pF
Nanofarads100 nF
Microfarads0.1 uF
Tolerance-

How it works

For a three-digit code, the value in picofarads is the first two digits multiplied by ten to the power of the third digit. A one or two-digit code is the value directly in picofarads. Divide picofarads by 1,000 for nanofarads, and again by 1,000 for microfarads. The tolerance letter shows how much the real value may differ.

Worked example

The code 104 reads as 10 times ten to the power of 4, which is 100,000 pF. Dividing by 1,000 gives 100 nF, and dividing again gives 0.1 uF. With a K tolerance letter the value is within plus or minus 10%, so between about 90 and 110 nF.

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Frequently asked questions

What does the capacitor code 104 mean?

On a 3-digit code the first two digits are the significant figures and the third is the number of zeros to add, giving a value in picofarads. So 104 is 10 followed by 4 zeros, which is 100,000 pF, equal to 100 nF or 0.1 uF.

How do I read a small capacitor code?

A 1 or 2 digit code is simply the value in picofarads, so 22 means 22 pF. A letter after the number is the tolerance, for example J is plus or minus 5%, K is plus or minus 10% and M is plus or minus 20%.

How do I convert pF, nF and uF?

There are 1,000 picofarads in a nanofarad and 1,000 nanofarads in a microfarad. So 100,000 pF is 100 nF, which is 0.1 uF. This calculator shows all three units at once so you can match whichever a circuit or part list uses.