Capacitor Number Code Calculator & How to Read

This calculator decodes the three- or four-digit code printed on most ceramic and film capacitors, returning the capacitance value in picofarads (pF), nanofarads (nF), and microfarads (µF). You enter the digits printed on the capacitor body, and the calculator applies the standard EIA code system to give you the value in three common units.

Formula

The capacitor number code uses a simple multiplier system. The first two digits are the significant figures, and the third digit is the multiplier in powers of 10. The result is in picofarads (pF).

Capacitance (pF) = (first two digits) × 10^(third digit)

For example, a code of 104 means 10 followed by 4 zeros: 10 × 10^4 = 100,000 pF = 100 nF = 0.1 µF.

For four-digit codes (e.g., 1005), the first three digits are the significant figures and the fourth is the multiplier: 100 × 10^5 = 10,000,000 pF = 10 µF.

Worked Example

Using the default code 104:

1. First two digits: 10
2. Third digit: 4, so multiplier is 10^4 = 10,000
3. Capacitance = 10 × 10,000 = 100,000 pF
4. Convert to nF: 100,000 pF ÷ 1000 = 100 nF
5. Convert to µF: 100,000 pF ÷ 1,000,000 = 0.1 µF

The calculator shows 100,000 pF, 100 nF, and 0.1 µF.

How the Capacitor Code System Works

Most small ceramic capacitors are too small to print the full value in microfarads, so manufacturers use a compact code. The system is based on the EIA-198 standard, which uses two significant digits and a multiplier. The code is always read in picofarads (pF), even if the final value is more conveniently expressed in nF or µF.

Here are common examples:

• 101 = 10 × 10^1 = 100 pF
• 222 = 22 × 10^2 = 2200 pF = 2.2 nF
• 473 = 47 × 10^3 = 47,000 pF = 47 nF
• 105 = 10 × 10^5 = 1,000,000 pF = 1 µF

Four-digit codes follow the same principle but use three significant digits. For instance, 1005 = 100 × 10^5 = 10,000,000 pF = 10 µF. This is common on higher-value capacitors where more precision is needed.

When to Use This Calculator

Use this calculator when you are repairing electronics, sorting a mixed bag of capacitors, or designing a circuit and need to verify the value of a part you have on hand. It is especially handy when you find a capacitor with a code like “104� and you are not sure whether it is 100 nF or 10 nF. The calculator eliminates the guesswork.

It also helps when you are replacing a capacitor and need to match the original value. Knowing the code’s meaning lets you cross-reference with a parts list or an online datasheet.

Common Mistakes and Misconceptions

A frequent error is reading the third digit as a direct multiplier instead of an exponent. For example, “104� is not 10 × 4 = 40 pF; it is 10 × 10^4 = 100,000 pF. Always treat the third digit as the power of ten.

Another mistake is confusing the code with the voltage rating. The number code only gives capacitance, not voltage. Voltage is usually printed separately (e.g., 50V, 100V) or may be absent on tiny parts.

Some capacitors use a different system: a letter and three digits, like “1A104� where “1A� is a voltage code (1A = 10V). The letter is not part of the capacitance code. Always separate the letter from the numeric code.

Also note that some capacitors use a “R� to indicate a decimal point, such as “4R7� meaning 4.7 pF. This is a non-standard but common marking. This calculator does not handle the “R� notation; you would need to interpret it manually.

Limitations of the Code System

The EIA code is primarily used on ceramic and film capacitors. Electrolytic capacitors usually have the value printed directly in µF (e.g., 10µF, 100µF) because they are large enough. Tantalum capacitors may use a color code or a numeric code with a voltage rating, but that is a different system.

Also, the code does not indicate tolerance. Tolerance is often given by a letter (e.g., J = ±5%, K = ±10%, M = ±20%) printed after the numeric code. For example, “104K� means 100 nF with ±10% tolerance. The calculator only decodes the numeric part.

Finally, the code does not give the capacitor’s voltage rating, temperature coefficient, or dielectric type. Those are printed separately or must be looked up from the manufacturer’s datasheet.

How to Read a Capacitor Code by Hand

If you do not have a calculator handy, you can decode the code manually:

1. Identify the first two (or three) digits as the significant figures.
2. Identify the last digit as the exponent (power of 10).
3. Write the significant figures, then add the number of zeros indicated by the exponent.
4. The result is in picofarads (pF).
5. Convert to nF by dividing by 1000, or to µF by dividing by 1,000,000.

For example, code “223� → 22 and 3 zeros → 22,000 pF → 22 nF. Code “475� → 47 and 5 zeros → 4,700,000 pF → 4.7 µF.

Frequently Asked Questions

What does the third digit mean on a capacitor code?

The third digit is the multiplier (exponent) in the formula: first two digits × 10^(third digit). So “104� means 10 × 10^4 = 100,000 pF. It is not a direct multiplier.

How do I convert pF to nF or µF?

1 nF = 1000 pF, and 1 µF = 1,000,000 pF. So divide the pF value by 1000 to get nF, or by 1,000,000 to get µF. For example, 100,000 pF = 100 nF = 0.1 µF.

What does a code like “4R7� mean?

The “R� indicates a decimal point. “4R7� means 4.7 pF. This is a common marking on small capacitors. The “R� takes the place of the decimal point.

Can I use this calculator for electrolytic capacitors?

No. Electrolytic capacitors are large enough to have their value printed directly in µF, so they do not use the EIA number code. This calculator is for ceramic and film capacitors that use the numeric code.

How do I know the voltage rating from the code?

You cannot. The number code only gives capacitance. Voltage is printed separately, often as a number and “V� (e.g., 50V). On tiny capacitors, voltage may be omitted entirely, and you must check the datasheet.

What if the code has a letter after the numbers, like “104K�?

The letter indicates tolerance: J = ±5%, K = ±10%, M = ±20%. The capacitance value is still 100,000 pF (100 nF). The letter does not affect the capacitance calculation.

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in code | Capacitor code (e.g. 104, 223, 475) | - | 104 | 0
out pf | Capacitance in pF | pF | 0 | 0
out nf | Capacitance in nF | nF | 0 | 0
out uf | Capacitance in µF | µF | 0 | 0