A capacitor is a circuit element that responds to rapidly changing signals. Capacitors store the energy from strong signals and can turn this energy into the circuit when needed. The most common use of capacitors is to filter noise, a fast-changing signal.
Different capacitor values are needed to capture different types of noise. Capacitor ratings are marked on the capacitor. Sometimes capacitance, voltage and tolerance are written directly on the capacitor, sometimes in the form of special codes.
In order to read the capacitor value, it is necessary to know the basic unit of capacitance, Farad (F). Farad indicates the ability of a capacitor to store electric charge. This value represents too large an amount to be used in an electronic circuit. For this reason, microfarad (µF), nanofarad (nF) and picofarad (pF) units, which express much smaller amounts, are used in capacitors. According to this; 1 µF represents 1×10–6 F, 1 nF equals 1×10–9 F, and 1 pF equals 1×10–12 F.
The capacitance value is often found on the capacitor as µF, nF or pF. No special effort is required to read them. Even if the letters µ, n are on the capacitor, the capacitance value in microfarads or nanofarads is shown. Special codes are used if the capacitor body is small and there is not enough space for marking.
If there is a two-digit number on the capacitor, it is the capacitance value in picofarads. If there is a three-digit number on the capacitor, the first two indicate the value of the capacitor, while the last digit indicates the multiplier (number of zeros). This shows the capacitance value in picofarads. Conversion can be done on nanofarad or microfarad scale when needed. As explained above, 1,000 pF equals 1 nF and 1,000 nF equals 1uF.
Like resistors, capacitors have a degree of tolerance. The tolerance value refers to the rate at which the actual capacitance is allowed to differ from the nominal value. The letter at the end of the three-digit code on the capacitor indicates the tolerance.
| Code | Capacitor Tolerance |
| B | ± 0.1% |
| C | ± 0.25% |
| D | ± 0.5% |
| F | ± 1% |
| G | ± 2% |
| H | ± 3% |
| J | ± 5% |
| K | ± 10% |
| M | ± 20% |
| Z | ± 80%, -20% |
For example; If 105J is written on a capacitor, the capacitance value of this capacitor is 1,000,000 pF. This is equivalent to 1 µF. The tolerance of this capacitor is ±5%. Similarly, if 102H is written on the capacitor, the capacitance value is 1,000 pF, that is 1 nF, and its tolerance is ±3%.
Another important characteristic for the capacitor is the maximum operating voltage. The maximum operating voltage is written directly on the capacitor in V or kV in most cases. In some capacitors, special codes are used to indicate the voltage. The voltage code can be above or before the capacitance code.
| 0G = 4.0V DC | 1J = 63V DC | 2D = 200V DC |
| 0L = 5.5V DC | 0k = 80V DC | 2P = 220V DC |
| 0J= 6.3V DC | 2A = 100V DC | 2E = 250V DC |
| 1A = 10V DC | 2Q = 110V DC | 2F = 315V DC |
| 1C = 16V DC | 2B = 125V DC | 2V = 350V DC |
| 1E = 25V DC | 2C = 160V DC | 2G = 400V DC |
| 1H = 50V DC | 2Z = 180V DC | 2W = 240V DC |
For example; If there is an 1H mark on a capacitor, the maximum operating voltage of this capacitor is 50V. A capacitor labeled 2A102J has a capacitance value of 1 nF, a tolerance of 5% and a maximum operating voltage of 100 V.
Capacitor codes clearly describe capacitance, tolerance and voltage. Knowing the capacitor codes is very important when choosing, comparing and replacing capacitors.
