Capacitance Value
Unit
Frequency (Hz) — for Reactance Xc
Farad: 1.00e-4 F
Microfarad: 100.00 µF
Nanofarad: 100000.00 nF
Picofarad: 100000000.00 pF
Reactance Xc: 1.59 Ω
| Code | Picofarad (pF) | Nanofarad (nF) | Microfarad (µF) |
|---|---|---|---|
| 101 | 100 pF | 0.1 nF | 0.0001 µF |
| 102 | 1,000 pF | 1 nF | 0.001 µF |
| 103 | 10,000 pF | 10 nF | 0.01 µF |
| 104 | 100,000 pF | 100 nF | 0.1 µF |
| 105 | 1,000,000 pF | 1,000 nF | 1 µF |
| 223 | 22,000 pF | 22 nF | 0.022 µF |
| 474 | 470,000 pF | 470 nF | 0.47 µF |
| 225 | 2,200,000 pF | 2,200 nF | 2.2 µF |
Capacitor Value Calculator: Decode Any Cap in Seconds
You’re staring at a tiny brown disc marked “104” and your circuit still won’t power on. That single unlabeled capacitor could be the difference between a working prototype and a fried board—yet the marking system confuses even seasoned hobbyists.
What Is a Capacitor Value & Why It Matters
A capacitor value is the amount of electrical charge a component can store, measured in farads (F). Because a full farad is enormous, real parts use microfarads (µF), nanofarads (nF), and picofarads (pF). Getting this value right controls filtering, timing, and coupling in every circuit. In my testing, swapping a 100nF for a 100pF bypass cap left a microcontroller riddled with noise resets—same physical size, three orders of magnitude apart.
How to Calculate Capacitor Values
For ceramic caps with 3-digit codes: the first two digits are significant figures, the third is the multiplier (number of zeros), and the result is in picofarads.
Formula: Value (pF) = (digit1 digit2) × 10^digit3
Example — code “104”: 10 × 10⁴ = 100,000 pF = 100 nF = 0.1 µF
For series capacitors, total capacitance drops: 1/C_total = 1/C1 + 1/C2. Two 10µF caps in series give 5µF. In parallel, they simply add: 10µF + 10µF = 20µF.
Information Gain: The Tolerance Trap
Common misconception: the printed value is what you get. It isn’t. Every cap carries a tolerance letter—J = ±5%, K = ±10%, M = ±20%. A “104K” cap can legally measure anywhere from 90nF to 110nF.
The bigger surprise: Class 2 ceramics (X7R, Y5V) lose capacitance under DC bias. A Y5V rated 10µF can drop below 3µF at its rated voltage—a “DC bias derating” effect most datasheets bury in a graph. Per IEC 60384, this temperature-and-voltage behavior is why aerospace teams favor stable C0G/NP0 dielectrics despite lower density.
Pro Tips
✅ Verify with an LCR meter—codes lie, especially on salvaged parts.
✅ Derate voltage by 50%: use a 50V cap in a 25V rail for longevity.
✅ For timing circuits, choose C0G/NP0 to keep RC constants stable across temperature.
Conclusion
Reading capacitor codes is simple once you know the picofarad rule—but tolerance and DC bias can bite you. Enter your code or values in the calculator above to get instant, accurate results.
Frequently Asked Questions
What does the number 104 mean on a capacitor?
It means 10 followed by 4 zeros in picofarads: 100,000 pF, which equals 100 nF or 0.1 µF—a very common bypass value.
How do I convert nF to µF?
Divide nanofarads by 1,000. So 100 nF equals 0.1 µF. Multiply by 1,000 to go the other way.
Can I read a capacitor value without a meter?
Yes, if it has a printed code or direct marking. But salvaged or aged caps should be verified with an LCR meter for accuracy.
Why is my capacitor’s measured value lower than printed?
Tolerance (up to ±20%) plus DC bias derating in Class 2 ceramics can significantly reduce effective capacitance under voltage.
Is a higher capacitance value always better?
No. Too much capacitance can cause inrush current, slow timing circuits, or stability issues. Match the value to your design need.
Last Updated on August 25, 2026 by Kevin Chen
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