Capacitor Code Calculator

Decode capacitor markings: 3-digit codes such as 104, tolerance letters, voltage codes such as 2A and 1H, and ceramic dielectric codes such as X7R and C0G, or find the code for a value.

Method, formulas and references

3-digit value code

The value is in picofarads: two significant digits and a power of ten. 104 = 10 × 10⁴ pF = 100 nF, 472 = 4.7 nF, 105 = 1 µF. A third digit of 9 multiplies by 0.1 and 8 by 0.01, so 479 = 4.7 pF; 7 is not used. A one- or two-digit number is the value in pF (47 = 47 pF).

(1)C = (first two digits) × 10^{third digit} pF

RKM notation

The letter replaces the decimal point and gives the unit: 4n7 = 4.7 nF, 2p2 = 2.2 pF, 100n = 100 nF, u47 = 0.47 µF. On small ceramic parts R is the decimal point in pF: 4R7 = 4.7 pF.

Tolerance and voltage

A letter after the value gives the tolerance: J = ±5 %, K = ±10 %, M = ±20 %, Z = +80 / −20 %. Below 10 pF, B, C and D are absolute: ±0.1, ±0.25 and ±0.5 pF. A two-character voltage code may come first: its digit is the decade and its letter the mantissa, so 1H = 50 V, 2A = 100 V and 2J = 630 V. 2A104J is therefore 100 nF, ±5 %, 100 V.

Surface-mount ceramic capacitors are usually not marked at all; their value is only on the reel label.

Dielectric codes (EIA-198)

Class 2 codes give the temperature range and the capacitance change over it: X7R is −55 to +125 °C with ±15 %. The first letter is the low temperature (X = −55, Y = −30, Z = +10 °C), the digit the high temperature (5 = +85, 6 = +105, 7 = +125 °C) and the last letter the change (R = ±15 %, S = ±22 %, V = +22 / −82 %). Class 2 capacitors also lose capacitance with DC bias, which the code does not show. Class 1 codes such as C0G (NP0) give a temperature coefficient: 0 ±30 ppm/K.

References

IEC 60062:2016, Marking codes for resistors and capacitors.
EIA-198 (RS-198), Ceramic dielectric capacitors classes I, II, III and IV.

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