How to Read the Numbers on a Capacitor

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Unlike resistors, capacitors employ a wide variety of codes to draw their characteristics. Physically small capacitors are peculiarly difficult to read, due to the limited space bachelor for printing. The information in this article should help you read almost all modern consumer capacitors. Don't exist surprised if your information is printed in a different order than the one described here, or if voltage and tolerance info is missing from your capacitor. For many low-voltage DIY circuits, the simply data yous demand is the capacitance.

1. 1

   Know the units of measurement. The base unit of capacitance is the farad (F). This value is much too big for ordinary circuits, so household capacitors are labeled with i of the following units:^{[ane] [two]}

   • 1 µF, uF, or mF = i microfarad = 10^-6 farads. (Careful — in other contexts, mF is the official abbreviation for millifarads, or 10^-3 farads.)
   • 1 nF = one nanofarad = 10^-9 farads.
   • one pF, mmF, or uuF = i picofarad = 1 micromicrofarad = 10^-12 farads.

2. 2

   Read the capacitance value. Most big capacitors have a capacitance value written on the side. Slight variations are common, so look for the value that most closely matches the units in a higher place. You may need to adjust for the following:

   • Ignore capital letters in the units. For example, "MF" is but a variation on "mf." (It is definitely non a megafarad, fifty-fifty though this is the official SI abbreviation.)
   • Don't get thrown past "fd." This is simply another abbreviation for farad. For example, "mmfd" is the same as "mmf."
   • Beware single-letter markings such as "475m," usually establish on smaller capacitors.^[3] See below for instructions.

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3. three

   Look for a tolerance value. Some capacitors listing a tolerance, or the maximum expected range in capacitance compared to its listed value. This isn't of import in all circuits, simply you may need to pay attention to this if you crave a precise capacitor value. For case, a capacitor labeled "6000uF +50%/-70%" could really have a capacitance as high every bit 6000uF + (6000 * 0.v) = 9000uF, or as low as 6000 uF - (6000uF * 0.7) = 1800uF.

   • If in that location is no percentage listed, look for a single letter of the alphabet after the capacitance value or on its own line. This may exist lawmaking for a tolerance value, described below.

4. 4

   Check the voltage rating. If there is room on the body of the capacitor, the manufacturer usually lists voltage as a number followed past a V, VDC, VDCW, or WV (for "Working Voltage").^[iv] This is the maximum voltage the capacitor is designed to handle.

   • ane kV = 1,000 volts.
   • See below if you suspect your capacitor uses a code for voltage (a unmarried letter of the alphabet or one digit and i alphabetic character). If in that location is no symbol at all, reserve the cap for low-voltage circuits only.
   • If you are edifice an Air conditioning circuit, look for a capacitor rated specifically for VAC. Practice not use a DC capacitor unless you have an in-depth knowledge of how to convert the voltage rating, and how to utilize that type of capacitor safely in AC applications.^[five]

5. 5

   Look for a + or - sign. If you encounter one of these adjacent to a concluding, the capacitor is polarized. Make sure to connect the capacitor'south + end to the positive side of the circuit, or the capacitor could eventually cause a brusque or even explode.^[vi] If in that location is no + or -, you can orient the capacitor either way.

   • Some capacitors use a colored bar or a ring-shaped depression to show polarity. Traditionally, this mark designates the - end on an aluminum electrolytic capacitor (which are unremarkably shaped like tin cans). On tantalum electrolytic capacitors (which are very small), this marker designates the + end.^[7] (Disregard the bar if it contradicts a + or - sign, or if it is on a non-electrolytic capacitor.)

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1. 1

   Write down the first two digits of the capacitance. Older capacitors are less anticipated, just almost all modern examples use the EIA standard lawmaking when the capacitor is also small to write out the capacitance in full. To start, write downwards the starting time two digits, and so determine what to practice side by side based on your code:^[8]

   • If your code starts with exactly two digits followed by a alphabetic character (eastward.k. 44M), the first two digits are the full capacitance code. Skip down to finding units.
   • If ane of the first two characters is a letter, skip downwards to letter systems.
   • If the start three characters are all numbers, continue to the next footstep.

2. 2

   Use the third digit as a zero multiplier. The three-digit capacitance code works as follows:

   • If the third digit is 0 through half dozen, add that many zeroes to the cease of the number. (For case, 453 → 45 x 10³ → 45,000.)
   • If the third digit is viii, multiply by 0.01. (e.g. 278 → 27 x 0.01 → 0.27)
   • If the third digit is 9, multiply by 0.ane. (e.1000. 309 → thirty x 0.1 → three.0)

3. 3

   Work out the capacitance units from context . The smallest capacitors (made from ceramic, film, or tantalum) use units of picofarads (pF), equal to x^-12 farads. Larger capacitors (the cylindrical aluminum electrolyte blazon or the double-layer type) use units of microfarads (uF or µF), equal to ten^{-half dozen} farads.^[9]

   • A capacitor may overrule this past adding a unit afterward it (p for picofarad, n for nanofarad, or u for microfarad). Still, if there is just ane letter after the code, this is usually the tolerance code, non the unit. (P and N are uncommon tolerance codes, but they do exist.)

4. iv

   Read codes that contain messages instead . If your code includes a letter as 1 of the first 2 characters, there are three possibilities:

   • If the letter is an R, replace it with a decimal point to go the capacitance in pF. For example, 4R1 means a capacitance of four.1pF.^[10]
   • If the letter is p, n, or u, this tells yous the units (pico-, nano-, or microfarad). Supplant this letter with a decimal point. For example, n61 means 0.61 nF, and 5u2 means five.2 uF.^[11]
   • A code like "1A253" is actually two codes. 1A tells you the voltage, and 253 tells yous the capacitance every bit described above.^[12]

5. 5

   Read the tolerance code on ceramic capacitors. Ceramic capacitors, which are commonly tiny "pancakes" with two pins, typically list the tolerance value as one letter immediately after the 3-digit capacitance value. This letter represents the tolerance of the capacitor, pregnant how shut the bodily value of the capacitor tin be expected to exist to the indicated value of the capacitor. If precision is important in your circuit, translate this lawmaking as follows:^[13]

   • B = ± 0.1 pF.
   • C = ± 0.25 pF.
   • D = ± 0.5 pF for capacitors rated below 10 pF, or ± 0.five% for capacitors above 10 pF.
   • F = ± 1 pF or ± 1% (aforementioned system as D above).
   • G = ± 2 pF or ± 2% (come across above).
   • J = ± v%.
   • K = ± x%.
   • M = ± 20%.
   • Z = +eighty% / -twenty% (If you meet no tolerance listed, presume this equally the worst case scenario.^[fourteen] )

6. 6

   Read alphabetic character-number-letter of the alphabet tolerance values. Many types of capacitors correspond the tolerance with a more detailed three-symbol organisation. Interpret this as follows:^[15]

   • The first symbol shows minimum temperature. Z = 10ºC, Y = -30ºC, 10 = -55ºC.
   • The 2nd symbol shows maximum temperature. 2 = 45ºC, iv = 65ºC, 5 = 85ºC, 6 = 105ºC, 7 = 125ºC.
   • The third symbol shows variation in capacitance across this temperature range. This ranges from the most precise, A = ±1.0%, to the to the lowest degree precise, Five = +22.0%/-82%. R, ane of the almost common symbols, represents a variation of ±15%.^[16]

7. 7

   Translate voltage codes . You can look upwardly the EIA voltage chart for a full listing, merely about capacitors utilise 1 of the following mutual codes for maximum voltage (values given for DC capacitors only):^[17]

   • 0J = 6.3V
   • 1A = 10V
   • 1C = 16V
   • 1E = 25V
   • 1H = 50V
   • 2A = 100V
   • 2D = 200V
   • 2E = 250V
   • 1 letter of the alphabet codes are abbreviations of one of the mutual values higher up. If multiple values could apply (such as 1A or 2A), yous'll need to work information technology out from context.
   • For an judge of other, less common codes, await at the commencement digit. 0 covers values less than ten; ane goes from ten to 99; ii goes from 100 to 999; and so on.

8. 8

   Look upward other systems. Sometime capacitors or capacitors made for specialist use may employ unlike systems. These are not included in this commodity, merely yous can apply this hints to guide your further research:

   • If the capacitor has i long code beginning with "CM" or "DM," look upwardly the U.Southward. military capacitor chart.
   • If there is no lawmaking but a series of colored bands or dots, await up the capacitor color code.^[xviii]

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• Always measure the capacitance if you aren't able to read the data on the capacitor.

• The capacitor tin also list information on operating voltages. The capacitor should support a higher voltage than the circuit you use it in; otherwise, it may break down (possibly explode) under performance

• 1,000,000 picoFarads (pF) equals one microFarad (µF). Many common capacitor values are near this crossover area and could exist commonly referred to using either unit designation. For example, a 10,000 pF cap is more commonly referred to as 0.01 uF.

• Although you tin't determine capacitance by the shape and size alone, you lot can gauge at a rough range based on how the capacitor is being used:

  • The largest capacitors in a tv monitor are in the power supply. Each one tin have a capacitance as high as 400 to 1,000 µF, which tin can be lethal if handled incorrectly.^{[19] [xx]}
  • The large capacitors in an antique radio typically range from 1-200 µF.^[21]
  • Ceramic capacitors are usually smaller than your thumb and adhere to the circuit with two pins. Used in many applications, they typically range from i nF to one µF, and occasionally up to 100 µF.^[22]

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• Exist very careful when handling large capacitors, which tin can concord a lethal amount of energy when charged. Always brand certain to discharge them starting time past using an appropriate resistor. Never brusk excursion them, as this could cause an explosion.

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Article Summary X

To read a large capacitor, first detect the capacitance value, which will exist a number or a number range most commonly followed past µF, Chiliad, or FD. So look for a tolerance value, typically listed as a percentage. Next, check the voltage rating, which is usually listed equally a number followed by the letters V, VDC, VDCW, or WV. Finally, see if your capacitor is polarized by looking for plus or minus signs side by side to its terminals, which indicate that information technology is. For more than on reading capacitors, including how to read compact capacitor codes, scroll downwards!

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