Capacitor Code Decoder
Decode 3-digit ceramic capacitor markings (like 104, 473, 222) into pF, nF, and µF. Supports EIA tolerance letters, voltage ratings, and reverse lookup from capacitance to code.
How to Use
- Type the 3-digit code printed on the capacitor (e.g., "104", "473", "222").
- Optionally add a tolerance letter (J = ±5%, K = ±10%, M = ±20%).
- The decoded value appears in pF, nF, and µF with the full tolerance range.
- Use "Reverse" mode to find the code for a given capacitance.
- The visualization shows how the code maps to the formula XY × 10^Z pF.
Show Work
Tolerance Codes (EIA)
The Formula
History of the Capacitor Marking Code
Ceramic and mica capacitors gained widespread use in radio and early electronics during the 1930s and 1940s, but their small physical size made printing full values like "0.0001 µF" impractical. The Electronic Industries Association (EIA, founded 1924 as RMA) standardized a shorthand: encode the capacitance in picofarads as two significant digits followed by a decimal multiplier, borrowing the same "digit-digit-exponent" idea already used for resistor color bands.
The scheme — "XYZ" meaning XY × 10Z picofarads — and its tolerance letter suffixes were formalized in EIA standards RS-198 (later RS-335) during the 1960s, and subsequently adopted into the international IEC 60062 standard used worldwide today. The same code now appears on surface-mount ceramic multilayer caps (MLCCs), through-hole disk ceramics, and film caps; electrolytics skip the code because their size allows full "100 µF 25 V" markings.
The stability of the convention over 60+ years is why a part marked "104" today still reads as 100,000 pF (0.1 µF) just as it would have in a 1965 receiver schematic — an unusually durable notation in a field that otherwise reinvents itself every decade.
About This Calculator
Enter a 2-, 3-, or 4-digit code with optional tolerance letter (e.g. 104, 473K, 1004F) and this tool decodes it to picofarads, nanofarads, and microfarads simultaneously — so you can match the reading to whatever unit your schematic uses. Switch to encode mode to go the other direction: type a value and get the printed code.
One gotcha the tool flags for you: a code like 100 is 10 pF (10 followed by zero extra zeros), not 100 pF. A code like 104 is 100,000 pF = 0.1 µF. That single trailing digit multiplies by 10× at a time, which catches a lot of people new to the system. All decoding runs in your browser; nothing is transmitted.
Frequently Asked Questions
How do I read a capacitor code?
Three-digit codes follow XYZ → XY × 10^Z picofarads. So 104 = 10 × 10^4 pF = 100,000 pF = 100 nF = 0.1 µF. Two-digit codes are read directly in pF (e.g., "22" = 22 pF).
What does the letter after the code mean?
EIA tolerance codes: J=±5%, K=±10%, M=±20%, Z=+80/−20%. So "104K" is 100nF ±10%. The letter is separate from the capacitance.
Why don't small capacitors have a decimal value printed?
There's not enough room on the body. Instead of printing 0.1 µF or 100 nF, manufacturers use the compact 3-digit code — always in picofarads — with the third digit being the multiplier exponent.
What about 4-digit codes?
Four-digit codes follow XYZW → XYZ × 10^W pF, giving more precision. Example: 1003 = 100 × 10^3 pF = 100 nF. Rare on ceramic caps but common on precision polyester/polypropylene types.
How do I identify the voltage rating?
Voltage is usually printed separately (e.g., "50V" or "2A" where A=1.0, B=1.25, etc. per EIA-198). Always pick a capacitor rated at 2× your circuit's max voltage for longevity.
What does a class code like X7R mean?
X7R, C0G/NP0, Y5V are dielectric classes that describe temperature stability. C0G is the most stable (and expensive); X7R is a common compromise; Y5V has high capacitance but poor stability. Class is printed alongside or near the value code.
Common Use Cases
Decoding a Bag of SMD Caps
Your bag labeled "104" arrived — verify these are the 100nF decoupling caps you ordered, not 100pF or 0.1µF by mistake.
Board Repair / Reverse Engineering
Reading the 3-digit code on an old PCB to match a replacement cap when the schematic is lost.
BOM Verification
Cross-checking a BOM entry like "0.1µF 50V X7R 0603" against the printed code on the datasheet footprint.
Through-Hole Kit Identification
Sorting a mixed bag of unmarked ceramic disk caps — read the printed codes to group them by value.
Teaching / Learning Electronics
Students decoding their first breadboard components. The formula XY × 10^Z becomes obvious after a few examples.
Tolerance Range Check
Verifying a "104K" cap (100nF ±10%) is 90–110nF — relevant for filter and timing circuits where tolerance matters.
Last updated: