Capacitor Code Decoder

What is capacitor code decoding?

Small ceramic and film capacitors use a numeric code printed on their body instead of writing the full capacitance value. The code typically consists of three digits: the first two digits are significant figures, and the third digit is the multiplier (power of 10) in picofarads. For example, the code 104 means 10 followed by four zeros = 100,000 pF = 100 nF = 0.1 uF.

This coding system exists because capacitors are often too small to print the full value legibly. Understanding the code lets you quickly identify components when building or repairing circuits. Electrolytic capacitors are large enough to print the value directly (like 100uF/25V), so they do not use this code system.

How the code works

The three-digit code is read in picofarads (pF). The first two digits are the value, and the third is the number of zeros to add. So 473 = 47 followed by 3 zeros = 47,000 pF = 47 nF. Some capacitors add a letter for tolerance: J = 5%, K = 10%, M = 20%. A voltage rating may also appear, like 473K 50V.

Understanding capacitance units: pF, nF, and µF

Capacitance is measured in farads (F), but a single farad is an enormous value rarely seen in electronics. Practical capacitors use three smaller units, each separated by a factor of 1,000:

• Picofarad (pF) — one trillionth of a farad (10⁻¹² F). The base unit used by the 3-digit code system. Small ceramic capacitors are typically in the pF range.
• Nanofarad (nF) — one billionth of a farad (10⁻⁹ F). Equal to 1,000 pF. Film and ceramic capacitors in timing and filter circuits are commonly expressed in nF.
• Microfarad (µF) — one millionth of a farad (10⁻⁶ F). Equal to 1,000 nF or 1,000,000 pF. Electrolytic and larger ceramic capacitors are typically rated in µF.

To convert between units, divide or multiply by 1,000. For example: 100,000 pF ÷ 1,000 = 100 nF, and 100 nF ÷ 1,000 = 0.1 µF. When in doubt, always convert to pF first using the 3-digit code, then move the decimal point as needed.

Worked decoding examples

The best way to become fluent with capacitor codes is to work through examples step by step. Here are three detailed walkthroughs covering the most common codes you will encounter:

Example 1: code 104

Digit 1 = 1, digit 2 = 0, so the significant figures are 10. Digit 3 = 4, meaning add 4 zeros. Result: 10 followed by 0000 = 100,000 pF. Converting: 100,000 pF ÷ 1,000 = 100 nF = 0.1 µF. This is the single most common decoupling capacitor value in digital electronics — you will find it across virtually every microcontroller circuit.

Example 2: code 223

Digit 1 = 2, digit 2 = 2, so the significant figures are 22. Digit 3 = 3, meaning add 3 zeros. Result: 22 followed by 000 = 22,000 pF. Converting: 22,000 pF ÷ 1,000 = 22 nF = 0.022 µF. You might see this marked as 223K on the body, where K indicates ±10% tolerance.

Example 3: code 472

Digit 1 = 4, digit 2 = 7, so the significant figures are 47. Digit 3 = 2, meaning add 2 zeros. Result: 47 followed by 00 = 4,700 pF. Converting: 4,700 pF ÷ 1,000 = 4.7 nF = 0.0047 µF. A capacitor marked 472J has ±5% tolerance, so its actual value falls between 4,465 pF and 4,935 pF.

Ceramic vs electrolytic capacitors

Ceramic and film capacitors are non-polarized — they can be installed in either direction — and they use the 3-digit code described above. They are physically small, which is why the shorthand code is necessary. Common types include MLCC (multi-layer ceramic capacitor), disc ceramic, and polyester film. Typical values range from 1 pF up to around 10 µF.

Electrolytic capacitors (aluminum or tantalum) are polarized and must be installed with the correct orientation — the negative lead is usually marked with a stripe or a minus sign, and the positive lead is longer. Because electrolytic capacitors are physically large enough to print legibly, they display their value and voltage rating directly on the body (for example, 100 µF 25V or 470 µF 16V). Do not try to apply the 3-digit code system to electrolytics — the number printed on them is already the capacitance in microfarads.

Voltage rating markings

In addition to the capacitance code and tolerance letter, many capacitors include a voltage rating — the maximum DC working voltage (WVDC) the component can safely handle. Exceeding the voltage rating risks dielectric breakdown and permanent damage. Voltage markings appear in several forms:

• Numeric suffix — for example, 104K50 means 100 nF, ±10% tolerance, 50 V rating.
• EIA letter code — a single letter replaces the numeric voltage: e.g. A = 10 V, B = 16 V, C = 25 V, D = 50 V, E = 63 V, F = 100 V. These letters can appear before or after the capacitance code depending on the manufacturer.
• Separate line — on larger capacitors, the voltage may be printed on a second line entirely: 100nF / 50V.

Common mistakes when reading capacitor codes

Even experienced engineers occasionally misread a capacitor. Here are the four mistakes that cause the most circuit failures:

• Confusing pF and nF — the 3-digit code always gives picofarads. If you read 104 as 104 nF instead of 100 nF, you will order a part that is 1,000× too large. Always decode to pF first, then convert.
• Ignoring polarity on electrolytics — installing an electrolytic capacitor backwards causes it to overheat, bulge, and potentially explode. Always identify the negative lead (the stripe side) before soldering.
• Treating a 0 multiplier as no zeros — the code 220 means 22 pF (multiply 22 by 10⁰ = 1, so no zeros are added). This is correct; 220 is not 2,200 pF. Similarly, 100 = 10 pF, not 100 pF.
• Ignoring the voltage rating — a 100 nF capacitor rated for 16 V will fail if used in a 24 V circuit. Always check the working voltage and derate by at least 20% for reliability.

How to use this tool

Enter the capacitor code (typically 1-3 digits) and the tool displays the capacitance in picofarads, nanofarads, and microfarads. You can also enter a capacitance value to find the corresponding code. The tool handles all standard codes including single and two-digit codes for very small values.

Common capacitor codes

• 104 = 100 nF (0.1 uF) — The most common decoupling capacitor value.
• 103 = 10 nF — Commonly used for filtering and timing.
• 102 = 1 nF — Used in high-frequency circuits.
• 224 = 220 nF (0.22 uF) — Popular in audio and coupling circuits.
• 105 = 1 uF — Large value for a ceramic capacitor.

Frequently asked questions

What do the letters after the code mean?

Letters indicate tolerance: J = plus/minus 5%, K = plus/minus 10%, M = plus/minus 20%, Z = +80/-20%. The letter may appear after the three-digit code. Some capacitors also include a voltage rating number or letter code.

Why do capacitors use picofarads as the base unit?

The three-digit code system uses picofarads because it allows most common capacitor values to be expressed as whole numbers without decimal points. Values from 1 pF to 99 uF can all be represented with a simple three-digit code, which is ideal for printing on small components.

Can a capacitor code have only two digits?

Yes. Very small capacitors (typically under 10 pF) sometimes use a two-digit code where the value in picofarads is printed directly — for example, 47 means 4.7 pF and 10 means 10 pF. Some manufacturers also use a decimal point, printing the value as 4p7 (4.7 pF) or n10 (100 pF). When in doubt, check the datasheet for the specific component series.

Why does the same capacitance appear on different capacitors with the same code but different physical sizes?

Physical size reflects voltage rating and capacitor technology, not capacitance alone. A 100 nF (104) ceramic capacitor rated for 50 V is physically larger than one rated for 10 V because the thicker dielectric needed for higher voltage takes up more space. Similarly, a 100 nF film capacitor is larger than a 100 nF MLCC because the film construction requires more material to achieve the same capacitance. When replacing a component, match both the capacitance code and the voltage rating.