About the Capacitor Code Calculator
This capacitor code calculator translates the tiny markings printed on ceramic, film and tantalum capacitors into a real value. Type the code exactly as printed — 104, 473K, 4n7, 4R7, 2A104J, 0.1 or 100nF — and it shows the capacitance in picofarads, nanofarads and microfarads, the tolerance letter, the EIA voltage code if there is one, and the minimum and maximum values the tolerance allows.
It is useful when sorting a parts drawer, repairing a circuit board, reading a schematic or ordering replacements. Switch to "Value → code" to go the other way: enter 100 nF or 2.2 µF and get the three-digit code (104, 225) you will see on the part.
Three-digit codes follow the EIA convention: the first two digits are significant figures and the third is the number of zeros to add, with the result in picofarads (8 and 9 mean ×0.01 and ×0.1). Letters such as R, p, n and µ mark the decimal point, a trailing letter gives the tolerance, and a digit-letter prefix such as 2A gives the rated voltage. Large electrolytic capacitors simply print their value and voltage.
How to use the capacitor code calculator
- 1Read the marking on the capacitor, including any letters before or after the digits.
- 2Type it exactly as printed (spaces are ignored, case does not matter).
- 3Read the value in pF, nF and µF plus tolerance and voltage.
- 4To find the code for a value, switch the direction to Value → code.
Formula and method
Small capacitors are too tiny for a full value, so manufacturers use the EIA numeric code. The first two digits are the significant figures and the third is a power-of-ten multiplier, always giving picofarads: 104 = 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. Third digits 8 and 9 are used for fractional multipliers (×0.01 and ×0.1), so 339 is 3.3 pF; 7 is not used.
Values below 10 pF often use R as a decimal point (4R7 = 4.7 pF), and many European parts use the unit letter as the decimal point (4n7 = 4.7 nF, p47 = 0.47 pF, 2µ2 = 2.2 µF). A trailing letter is the tolerance (J = ±5%, K = ±10%, M = ±20%, Z = +80/−20%), and a leading digit-letter pair such as 1H or 2A is the EIA voltage code (50 V and 100 V).
- pF
- Picofarad, 10⁻¹² F
- nF
- Nanofarad, 10⁻⁹ F = 1,000 pF
- µF
- Microfarad, 10⁻⁶ F = 1,000 nF
- J, K, M
- Tolerance letters ±5%, ±10%, ±20%
Worked examples
Ceramic capacitor marked 104
10 followed by four zeros is 100,000 pF. Dividing by 1,000 gives 100 nF, and again by 1,000 gives 0.1 µF — the classic decoupling capacitor.
Film capacitor marked 2A473J
2A is the EIA code for 100 V. 473 = 47 × 10³ = 47,000 pF = 47 nF, and J means ±5%, so the real value is between 44.65 nF and 49.35 nF.
Small values: 4R7 and 479
R stands in for the decimal point, so 4R7 is 4.7 pF. The same value can also be marked 479 (47 × 0.1 pF), because a third digit of 9 means multiply by 0.1.
European marking 4n7K
The n marks the decimal point in nanofarads, so 4n7 = 4.7 nF = 4,700 pF (EIA code 472). K means ±10%, giving 4.23 nF to 5.17 nF.
Code for a 2.2 µF capacitor
2.2 µF is 2,200,000 pF: significant figures 22 followed by five zeros, so the code is 225.
Frequently asked questions
What does 104 mean on a capacitor?+
104 means 10 followed by four zeros picofarads: 100,000 pF, which is 100 nF or 0.1 µF. It is the most common decoupling capacitor value in digital circuits.
What do the letters J, K and M mean on a capacitor?+
They are tolerance codes: J is ±5%, K is ±10% and M is ±20%. Z means +80%/−20%, common on cheap ceramic capacitors, while B, C and D give absolute tolerances of ±0.1, ±0.25 and ±0.5 pF for small values.
How do I convert pF to nF and µF?+
Divide picofarads by 1,000 to get nanofarads and by 1,000,000 to get microfarads. So 4,700 pF = 4.7 nF = 0.0047 µF, and 220 nF = 0.22 µF.
What is the voltage code 2A or 1H on a capacitor?+
It is the EIA voltage code: the digit gives the decade and the letter the value. Common ones are 1C = 16 V, 1E = 25 V, 1H = 50 V, 2A = 100 V, 2E = 250 V and 2J = 630 V.
What does 4n7 mean?+
In the IEC 60062 style the unit letter replaces the decimal point, so 4n7 is 4.7 nF (4,700 pF). Likewise 1µ0 is 1.0 µF, 220n is 220 nF and p68 is 0.68 pF.