Disc Capacitor Code Calculator & Decoder

This calculator decodes the three-digit code printed on ceramic disc capacitors into a capacitance value in picofarads (pF), nanofarads (nF), and microfarads (µF). You enter the code (e.g., 104, 222, 471) and optionally the tolerance letter; you get the capacitance in all common units, plus the tolerance percentage. The first two digits are the significant figures, the third digit is the multiplier (number of zeros), and the result is always in picofarads unless the code says otherwise.

Formula

The standard EIA-198 ceramic disc code uses three digits: AB C. The first two digits (A and B) are the significant figures, and the third digit (C) is the multiplier as a power of 10. The capacitance in picofarads is:

C (pF) = (10 × A + B) × 10^C

Where:

• A = first digit (1-9)
• B = second digit (0-9)
• C = third digit (0-9), representing the number of zeros to add

For example, code 104 means 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. Code 222 means 22 × 10² pF = 2,200 pF = 2.2 nF. Code 471 means 47 × 10¹ pF = 470 pF.

Tolerance letters follow the EIA standard: J = ±5%, K = ±10%, M = ±20%, Z = +80%/-20%. The calculator returns the numeric percentage for J, K, M, and Z; other letters (like C, D, F, G, H) are less common on disc ceramics but follow the same letter system used on other capacitors.

Worked Example

Using the default code 104 and tolerance K:

1. Split the code: first two digits = 10, third digit = 4.
2. Multiplier = 10⁴ = 10,000.
3. Capacitance = 10 × 10,000 = 100,000 pF.
4. Convert to nF: 100,000 / 1,000 = 100 nF.
5. Convert to µF: 100,000 / 1,000,000 = 0.1 µF.
6. Tolerance K = ±10%.

The calculator shows 100,000 pF, 100 nF, 0.1 µF, and ±10%.

How to Read a Disc Capacitor Code

Ceramic disc capacitors are small, round, often yellow or blue, with a code printed on one side. The code is almost always three digits, but you may also see:

• Two digits – e.g., “22� means 22 pF (no multiplier, third digit is implicitly 0).
• Four digits – e.g., “1000� means 100 × 10⁰ pF = 100 pF (the fourth digit is the multiplier).
• R notation – e.g., “4R7� means 4.7 pF; the R acts as a decimal point.
• No code – very small capacitors may have no marking; you must measure them with an LCR meter.

The unit is always picofarads unless the code contains a letter like “n� (nanofarads) or “µ� (microfarads), which is rare on disc ceramics but common on film capacitors.

Common Mistakes and Misconceptions

• Assuming the third digit is a value, not a multiplier. “104� is not 104 pF; it’s 100,000 pF. This is the most common error.
• Mixing up nF and pF. 1 nF = 1,000 pF, so 100 nF = 100,000 pF. A 104 capacitor is 100 nF, not 10 nF.
• Ignoring tolerance. A “Z� tolerance capacitor can be +80%/-20%, meaning a 100 pF cap could be anywhere from 80 to 180 pF. Always check the letter if the circuit is sensitive.
• Confusing voltage rating with capacitance. The voltage rating (e.g., 50V, 100V) is often printed separately or not at all on small discs. The code only gives capacitance and tolerance.

When to Use This Calculator

Use this calculator when you are:

• Replacing a ceramic disc capacitor in a radio, TV, or power supply and need to know its value.
• Sorting a mixed bag of capacitors and want to quickly identify values.
• Designing a circuit and need to confirm that a salvaged capacitor matches the schematic.
• Studying electronics and practicing code reading.

The calculator works for standard EIA three-digit codes. It does not decode military codes (e.g., “CK05�) or obsolete color bands. For those, consult a capacitor code chart or datasheet.

Limitations of the Code System

The three-digit code is ambiguous for values below 10 pF. For example, code “100� could mean 10 × 10⁰ = 10 pF, but some manufacturers use “100� to mean 100 pF (as a four-digit code with an omitted trailing zero). In practice, most disc capacitors below 10 pF are marked with just two digits or with an R (e.g., “1R0� for 1.0 pF). If you see “100� on a disc, it is almost always 10 pF, but measuring with an LCR meter is the only sure way.

Another limitation: the code does not tell you the voltage rating, temperature coefficient (e.g., X7R, C0G), or dielectric type. Those are usually printed separately or can be inferred from the color (blue often means C0G/NP0, yellow often means X7R, but this is not guaranteed). For critical applications, always check the datasheet or measure the part.

Frequently Asked Questions

What does “104� mean on a capacitor?

“104� means 10 × 10⁴ picofarads = 100,000 pF = 100 nF = 0.1 µF. The first two digits are 10, the third digit (4) tells you to add four zeros.

How do I convert pF to nF or µF?

Divide by 1,000 to go from pF to nF (1 nF = 1,000 pF). Divide by 1,000,000 to go from pF to µF (1 µF = 1,000,000 pF). For example, 470 pF = 0.47 nF = 0.00047 µF.

What if the capacitor has only two digits?

Two digits mean the value is directly in picofarads. “22� is 22 pF, “47� is 47 pF. There is no multiplier digit.

What does the letter “K� mean on a disc capacitor?

“K� is the tolerance code meaning ±10%. Other common letters: J = ±5%, M = ±20%, Z = +80%/-20%. The letter is usually printed after the three-digit code.

Can I use this calculator for film capacitors too?

Yes, film capacitors often use the same three-digit code, but the unit may be nanofarads instead of picofarads if the code contains an “n� (e.g., “1n0� = 1.0 nF). This calculator assumes picofarads, which is standard for disc ceramics. For film caps, check the printed unit.

Why does my capacitor have no code at all?

Very small capacitors (e.g., 0402 or 0603 SMD) often have no marking. Even some through-hole discs may be unmarked if they are low-value or old. You must measure them with an LCR meter or multimeter with capacitance measurement.

Related

• Us Aggregate Stone Calculator: How It Works
• Fix Ugly iPhone 5 Scratches: Free & Easy Solutions
• Stone Yardage Calculator: How to Estimate Tons

in code | Capacitor code | - | 104 | 0
in tol | Tolerance letter | - | K | 0
out cap_pf | Capacitance | pF | 10^((floor(log10(code))-1)) * (floor(code/10^(floor(log10(code))-1))) * 10^(mod(code,10)) | 0
out cap_nf | Capacitance | nF | cap_pf / 1000 | 3
out cap_uf | Capacitance | µF | cap_pf / 1000000 | 6
out tol_pct | Tolerance | % | (tol=="J")*5 + (tol=="K")*10 + (tol=="M")*20 + (tol=="Z")*80 | 0