# How to Read a Capacitor

The base unit of capacitance is the farad (F). This value is much too large for ordinary circuits, so household capacitors are labeled with nF, µF, or mF. In the following article we will deep dive to understand how to read a capacitor.

## Polarised Capacitor

### Electrolytic Capacitors

Electrolytic capacitors are polarised andthey must be connected the correct way round, at least one of their leads will be marked + or -. They are not damaged by heat when soldering.

There are two designs of electrolytic capacitors;axialwhere the leads are attached to each end (4700µF in picture) andradialwhere both leads are at the same end (47µF in picture). Radial capacitors tend to be a little smaller and they stand upright on the circuit board.

It is easy to find the value of electrolytic capacitors because they are clearly printed with their capacitance and voltage rating. The voltage rating can be quite low (6V for example) and it should always be checked when selecting an electrolytic capacitor.

### Tantalum Bead Capacitors

Tantalum bead capacitors are polarised and have low voltage ratings like electrolytic capacitors. They are expensive but very small, so they are used where a large capacitance is needed in a small size.

Modern tantalum bead capacitors are printed with their capacitance, voltage and polarity in full. However older ones use a colour-code system which has two stripes (for the two digits) and a spot of colour for the number of zeros to give the value in µF.

The standard colour code is used, but for the spot,greyis used to mean × 0.01 andwhitemeans × 0.1 so that values of less than 10µF can be shown.

A third colour stripe near the leads shows the voltage (yellow 6.3V, black 10V, green 16V, blue 20V, grey 25V, white 30V, pink 35V). The positive (+) lead is to the right when the spot is facing you: ‘when the spot is in sight, the positive is to the right.

#### Capacitor Colour Code

Colour coding table of capacitors

 Colour Significant digits Multiplier Capacitance tolerance Black 0 1 ±20% Brown 1 10 ±1% Red 2 100 ±2% Orange 3 1000 — Yellow 4 10000 — Green 5 — ±0.5% Blue 6 — — Violet 7 — — Grey 8 — — White 9 — — Gold — — ±5%* Silver — — ±10%

For example: blue, grey, black spot means 68µF
For example: blue, grey, white spot means 6.8µF
For example: blue, grey, grey spot means 0.68µF

## Unpolarised Capacitors (small values, up to 1µF)

Small value capacitors are unpolarised and may be connected either way round. They are not damaged by heat when soldering, except for one unusual type (polystyrene). They have high voltage ratings of at least 50V, usually 250V or so.

It can be difficult to find the values of these small capacitors because there are many types of them and different labelling systems.

Many small value capacitors have their value printed but without a multiplier,

For example0.1means 0.1µF = 100nF.

Sometimes the multiplier is used in place of the decimal point:
For example: 4n7means 4.7nF.

### Capacitor Number Code

A number code is often used on small capacitors where printing is difficult:

• the 1st number is the 1st digit,
• the 2nd number is the 2nd digit,
• the 3rd number is the number of zeros to give the capacitance in pF.
• Ignore any letters – they just indicate tolerance and voltage rating.

For example: 102means 1000pF = 1nF (not 102pF!)

For example: 472Jmeans 4700pF = 4.7nF (J means 5% tolerance).

## Some Solved Numerical on Capacitor Value

Capacitor Letter Codes Table

 S.N. Code Picofarad Nanofarad Microfarad (pF) (nF) (uF) 1 100 10 0.01 0.00001 2 150 15 0.015 0.000015 3 220 22 0.022 0.000022 4 330 33 0.033 0.000033 5 470 47 0.047 0.000047 6 101 100 0.1 0.0001 7 121 120 0.12 0.00012 8 131 130 0.13 0.00013 9 151 150 0.15 0.00015 10 181 180 0.18 0.00018 11 221 220 0.22 0.00022 12 331 330 0.33 0.00033 13 471 470 0.47 0.00047 14 561 560 0.56 0.00056 15 681 680 0.68 0.00068 16 751 750 0.75 0.00075 17 821 820 0.82 0.00082 18 102 1000 1 0.001 19 152 1500 1.5 0.0015 20 202 2000 2 0.002 21 222 2200 2.2 0.0022 22 332 3300 3.3 0.0033 23 472 4700 4.7 0.0047 24 502 5000 5 0.005 25 562 5600 5.6 0.0056 26 682 6800 6.8 0.0068 27 103 10000 10 0.01 28 153 15000 15 0.015 29 223 22000 22 0.022 30 333 33000 33 0.033 31 473 47000 47 0.047 32 683 68000 68 0.068 33 104 100000 100 0.1 34 154 150000 150 0.15 35 254 200000 200 0.2 36 224 220000 220 0.22 37 334 330000 330 0.33 38 474 470000 470 0.47 39 684 680000 680 0.68 40 105 1000000 1000 1 41 155 1500000 1500 1.5 42 205 2000000 2000 2 43 225 2200000 2200 2.2 44 335 3300000 3300 3.3