calculator
Capacitor code calculator
Most hobby capacitors are too small to print a value in µF, so the maker paints a three-digit number on the body instead. Type that number and this reads the value. Type a value and it shows the code you're looking for.
The capacitor
100 nF ±10%
That's 0.1 µF, 100 nF, or 100,000 pF — the same capacitor, three ways to write it.
- Digits 10 are the significant figures.
- Multiplier digit 4 means × 10 000.
- Value: 10 × 10 000 = 100 000 pF
- R marks the decimal point: 4R7 → 4.7 pF
- Two-digit code: 22 pF
- Tolerance letter K = ±10%.
How the three-digit code works
The number you see is almost always three digits — 1 0 4, 2 2 3, 4 7 5. The first two digits are the significant figures. The third digit is the multiplier: it says how many zeros to add. The whole value is in picofarads — the smallest capacitance unit you'll see on a hobby bench.
So 104 is 10 × 10⁴ pF = 100 000 pF. That's the same as 100 nF or 0.1 µF.
Three different units, exactly one capacitor. The unit people use depends on which number reads cleanly: 0.0000001 F
is accurate but hopeless to say out loud, so everyone writes 100 nF instead.
The tolerance letter
A letter after the digits — 104K, 223J, 472M — tells you how close
the real part is to the printed value. J is ±5%, K is ±10%, M is ±20%.
For timing circuits (the 555, filters, the RC time constant) you want J or K. For a bypass capacitor
— a cap sitting across power rails to kill noise — M is fine; the exact value doesn't matter, just that it's there.
Small values: two digits and R-decimal
Capacitors below 100 pF often skip the multiplier. A disc marked 22 is 22 pF; 47 is 47 pF.
For values with a decimal — the little NP0 caps you see across a 555's reset pin — the letter R marks the point:
4R7 means 4.7 pF, 1R0 means 1.0 pF. R stands in for the decimal because paint
on a tiny disc doesn't render dots clearly.
Common capacitor codes
| Code | Picofarads | Nanofarads | Microfarads | Where it shows up |
|---|---|---|---|---|
22 | 22 pF | 0.022 nF | — | Crystal load caps, high-frequency filters. |
101 | 100 pF | 0.1 nF | — | RF bypass, audio filter corners. |
102 | 1 000 pF | 1 nF | — | Timing R·C ≈ 100 µs with a 100 k resistor. |
103 | 10 000 pF | 10 nF | 0.01 µF | Debounce caps on buttons. |
104 | 100 000 pF | 100 nF | 0.1 µF | The standard bypass cap. Default on every logic chip's VCC pin. |
105 | 1 000 000 pF | 1 000 nF | 1 µF | Low-pass audio filters, slow-rising ramps. |
475 | 4 700 000 pF | 4 700 nF | 4.7 µF | Bulk bypass next to a buzzer or motor driver. |
4R7 | 4.7 pF | — | — | Oscillator tuning, antenna matching. |
Common questions
My capacitor says 100n or 0.1 instead of a code. Film and electrolytic
capacitors often print the value directly — 100n is 100 nF, 0.1 µF is 0.1 µF, same cap. The
three-digit code is mostly for ceramics (discs, MLCCs) where there's no room for units.
What about the voltage rating? That's the other number on the body — 50V, 63V,
100V. It's the maximum voltage the cap can take across its leads. For a 9 V battery project any
16 V-or-higher cap is safe. Electrolytics are polarised; ceramics aren't. See
the 100 nF capacitor part page for the full picture.
My code has four digits. Precision caps use four digits — first three are significant figures,
the fourth is the multiplier. 1002 = 100 × 10² pF = 10 nF. These are rare on a hobby bench; three-digit
codes cover almost everything.
Use the value you decoded in the 555 timer frequency or RC time constant calculator, or read the companion resistor color code calculator for the resistor markings that live right next to it on the breadboard.