Content

• To step
• Method 1 of 2: Reading large capacitors
• Method 2 of 2: Read compact capacitor codes
• Tips
• Warnings

Unlike resistors, capacitors have a wide variety of codes for describing their characteristics. Physically small capacitors are especially difficult to read due to the limited space available for the code. The information in this article is intended to help you read almost all modern commercially available capacitors.Don't be surprised if the information on a capacitor is in a different order from the one described here, or if voltage and tolerance info is missing from your capacitor. For many home-made low-voltage circuits, the only information you need is capacitance.

To step

Method 1 of 2: Reading large capacitors

1. Know which units are being used. The SI unit of capacity is the farad (F). This value is far too large for regular circuits, so they are labeled according to one of the following units:
   • 1 µF, uF or mF = 1 microfarad = 10 farad (careful - in another context, mF officially means millifarad, or 10 farad).
   • 1 nF = 1 nanofarad = 10 farad.
   • 1 pF, mmF, or uuF = 1 picofarad = 1 micromicrofarad = 10 farad.
2. Read the value of the capacity. The capacity of most large capacitors is written on the side. Slight variations are common, so look for the value that most closely matches the above units. Possible variations you may encounter are:
   • Ignore capital letters in the units. For example, "MF" is just a variation of "MF". (It is certain no megafarad, even though it is the official SI abbreviation).
   • Don't be confused by "fd". This is just another shorthand for farad. For example, "mmfd" is the same as "mmf".
   • Look for single letter markings, such as "475m", usually on smaller capacitors. See below for instructions.
3. Find the tolerance value. Some capacitors specify a tolerance, or the maximum capacitance range compared to the stated value. This doesn't matter for all circuits, but you should pay attention to this if you need an accurate capacitor reading. For example, a capacitor labeled '6000 uF +50% / - 70%' can have actual capacitance as low as 6000 uF + (6000 * 0.5) = 9000 uF, or as low as 6000 uF - (6000 uF * 0.7) = 1800 µF.
   • If no percentage is given, look for a single letter after the capacity value or on its own line. This can be the code for a tolerance level, as described below.
4. Check the voltage. If there is space on the solid part of the capacitor, the manufacturer usually lists a voltage as the number, followed by a V, VDC, VDCW or WV (for "Working Voltage"). This is the maximum voltage that the capacitor can handle.
   • 1 kV = 1,000 volts.
   • See below if you suspect that your capacitor uses a code for the voltage (a single letter or a number and a letter). If there is no symbol at all, use the top only on low voltage circuits.
   • If you are building an AC circuit, look for a capacitor specifically designed for VAC. Do not use a DC capacitor unless you have in-depth knowledge of voltage conversion and how to use that type of capacitor safely in AC applications.
5. Find a plus or minus sign. If you see one of these next to a terminal, then the capacitor is polarized. Make sure to connect the plus side of the capacitor to the positive side of the circuit, otherwise the capacitor could eventually short or even explode. If you don't see a plus or minus sign, you can connect the capacitor in both ways.
   • Some capacitors have a colored bar or stanchion notch to indicate polarity. Typically, this marking indicates the negative terminal of an aluminum electrolytic capacitor, or electrolytic capacitor, (which is usually shaped like cans). On a tantalum capacitor (which is very small), this marking indicates the plus pole. (ignore the bar if it contradicts a + or - sign, or if it is not an capacitor).

Method 2 of 2: Read compact capacitor codes

1. Write down the first two digits of the capacity. Older capacitors are less predictable, but almost all modern examples use the EIA standard code when the capacitor is too small to fully write the capacitance. To start, write down the first two numbers, then decide what to do next based on the code:
   • If the code starts with exactly two digits followed by a letter (such as 44M), the first two digits are the full capacity code. Continue to determine the units.
   • If one of the first two characters is a letter, continue with letter systems.
   • If the first three characters are all numbers, proceed to the next step.
2. Use the third digit as a zero multiplier. The three-digit capacity code works as follows:
   • If the third digit is 0-6, add that number of zeros to the end of the number. (For example: 453 → 45 x 10 → 45000.)
   • If the third digit is 8, multiply by 0.01. (e.g. 278 → 27 x 0.01 → 0.27)
   • If the third digit is 9, multiply by 0.1. (e.g. 309 → 30 x 0.1 → 3.0)
3. Determine the units of the capacity from the context. The smallest capacitors (made of ceramic, film, or tantalum) have the unit picofarad (pF), equal to 10 farad. Larger capacitors (the cylindrical aluminum elco or the one with a double layer) have the unit microfarad (uF or µF), equal to 10 farad.
   • A capacitor can override this by placing a unit behind it (p for picofarad, n for nanofarad, or u for microfarad). However, if there is no more than one letter after the code, this is usually the tolerance code, and not a unit. (P and N are not common tolerance codes, but they do exist).
4. Read codes with letters. If your code contains a letter as one of the first two characters, there are three possibilities:
   • If the letter is an R, replace it with a decimal point to get the capacitance in pF. For example: 4R1 means a capacitance of 4.1pF.
   • If the letter is p, n or u, then this gives you the units (pico, nano or microfarad). Replace this letter with a decimal point. For example, n61 means 0.61 nF and 5u2 means 5.2 uF.
   • A code such as "1A253" actually consists of two codes. 1A represents voltage and 253 represents capacitance as described above.
5. Read the tolerance codes on ceramic capacitors. Ceramic capacitors, which usually look like very small "pancakes" with two pins, generally indicate the tolerance value as a letter immediately after the capacitance value made up of those numbers. This letter represents the tolerance of the capacitor, and indicates how close the actual value of the capacitor is likely to be to the indicated value of the capacitor. If accuracy is important in your circuit, translate this code as follows:
   • B = ± 0.1 pF.
   • C = ± 0.25 pF.
   • D = ± 0.5 pF for capacitors below 10 pF, or ± 0.5% for capacitors above 10 pF.
   • F = ± 1 pF or ± 1% (same system as D above).
   • G = ± 2 pF or ± 2% (see above).
   • J = ± 5%.
   • K = ± 10%.
   • M = ± 20%.
   • Z = + 80% / -20% (If you do not see a tolerance value, take this as the worst case scenario.
6. Read letter-number-letter tolerance values. Many types of capacitors indicate tolerance with a more detailed three-symbol system. Interpret it as follows:
   • The first symbol indicates the minimum temperature. Z = 10ºC, Y = -30ºC, X = -55ºC.
   • The second symbol indicates the maximum temperature. 2 = 45ºC, 4 = 65ºC, 5 = 85ºC, 6 = 105ºC, 7 = 125ºC.
   • The third symbol indicates the variation in capacity over this temperature range. This range goes from the most accurate, a = ± 1.0%, to the least accurate, V. = +22,0%/-82%. R. is one of the most common symbols and represents a deviation of ± 15%.
7. Interpret the voltage codes. You can look up the EIA voltage table for a full list, but most capacitors use one of the following common maximum voltage codes (values ​​are given for DC capacitors only):
   • 0J = 6.3V
   • 1A = 10V
   • 1C = 16V
   • 1E = 25V
   • 1H = 50V
   • 2A = 100V
   • 2D = 200V
   • 2E = 250V
   • Letter codes are abbreviations of one of the common values ​​listed above. If multiple values ​​may apply (such as 1A or 2A), then you have to take out of context which one you need.
   • For an estimate of other lesser-known codes, look at the first digit. Zero (0) represents values ​​less than ten; 1 goes from 10 to 99; 2 ranges from 100 to 999; and so on.
8. Check out other systems. Old capacitors or those made for specialist applications may use different systems. These are not included in this article, but you can use the following hints as a guide for further research:
   • If the capacitor has a long code starting with "CM" or "DM," look it up in the "U.S. military's capacitor table.
   • If there is no code but a series of colored bands or dots, look up the color codes of capacitors.

Tips

• The capacitor can also contain a list of information about the operating voltages. The capacitor must support a higher voltage than the circuit you are going to use it in, otherwise it could break (or even explode) during application.
• 1,000,000 picoFarad (pF) equals 1 microFarad (µF). Common capacitor values ​​are in the vicinity of this transition area and are usually indicated by the unit. For example, a peak value of 10,000 pF is more commonly known as 0.01 uF.
• While you can't determine capacitance by shape and size alone, you can make a rough estimate based on how the capacitor is used:
  • The largest capacitors in a TV monitor are in the power supply. Each of these can have capacities as high as 400 to 1000 µF, which can be fatal if handled incorrectly.
  • The large capacitors in an antique radio usually range from 1 to 200 µF.
  • Ceramic capacitors are usually smaller than your thumb and attach to the circuit with two pins. They are used in many applications, typically ranging from 1 nF to 1 µF, and occasionally up to 100 µF.

Warnings

• Be very careful when working with large capacitors as they can hold a deadly amount of energy. Always discharge it first using a suitable resistor. Never short circuit them, as this could result in an explosion.