Capacitor Code Calculator

About the Capacitor Code Calculator

Capacitors are marked with short codes instead of a full value. Type what is printed on the part — 104, 473J, 2A104J, 4n7, 0.1µF 50V or X7R — and the calculator reads every part of it: the capacitance (shown in pF, nF and µF at once), the tolerance letter, the rated-voltage code and the ceramic dielectric class. Markings that can mean more than one thing get every reading, so you can compare with the part in your hand.

It works the other way too: enter a value such as 4.7 nF and get its three-digit code (472), its RKM code (4n7), its two-character chip code and, with a voltage, the film-capacitor style marking (2A472J). The codes follow IEC 60062 (value and tolerance codes) and EIA-198 (ceramic dielectric codes).

The capacitance codes

• Three digits (the most common): two significant figures and the number of zeros, in picofarads — 104 = 10 × 10⁴ pF = 100 nF, 222 = 2.2 nF, 101 = 100 pF. A last digit of 9 means ×0.1 and 8 means ×0.01, for values below 10 pF (109 = 1 pF, 339 = 3.3 pF). On tantalum and electrolytic chips the code reaches microfarads: 106 = 10 µF, 476 = 47 µF.
• R as the decimal point for small values in pF: 4R7 = 4.7 pF, R50 = 0.5 pF.
• RKM code (IEC 60062): the prefix letter takes the place of the decimal point — 4n7 = 4.7 nF, n47 = 0.47 nF (470 pF), 2u2 or 2µ2 = 2.2 µF, µ47 = 0.47 µF, 2F2 = 2.2 F.
• Value with unit: 0.1 µF, 100 nF, 47 pF, 2,200 µF. A comma before three digits is a thousands separator (10,000 pF = 10 nF); otherwise it is a decimal comma (4,7 nF). On old parts, MFD or MF means microfarad and MMFD, PFD or µµF means picofarad.
• Plain numbers on older parts: a whole number (47) is usually pF, a decimal (.047) usually µF; 10/16 on a small electrolytic means 10 µF, 16 V.
• Two-character code on tiny chips (EIA-198, IEC 60062 Annex B): a letter for the E24 figures (A = 1.0, B = 1.1 … S = 4.7 … Z = 9.1) and a digit for the power of ten in pF — S3 = 4.7 nF. Most chip capacitors carry no marking at all.

Tolerance letters (IEC 60062)

• B ±0.1%, C ±0.25%, D ±0.5%, F ±1%, G ±2%, J ±5%, K ±10%, M ±20%
• Asymmetric: Q −10/+30%, T −10/+50%, S −20/+50%, Z −20/+80%
• For capacitors below 10 pF the letters mean picofarads instead: B ±0.1 pF, C ±0.25 pF, D ±0.5 pF, F ±1 pF, G ±2 pF.
• A means a tolerance agreed with the maker (see the datasheet).
• Larger parts often print the tolerance in full — ±10%, −20/+80% or ±0.25 pF. The calculator reads those too and names the matching letter.

Rated-voltage codes

Japanese manufacturers’ part numbers and many film capacitors use a digit and a letter: the letter is a preferred number (A 1.0, B 1.25, C 1.6, D 2.0, E 2.5, F 3.15, G 4.0, H 5.0, J 6.3, K 8.0, plus V 3.5 and W 4.5) and the digit is the power of ten. So 0J = 6.3 V, 1A = 10 V, 1C = 16 V, 1E = 25 V, 1V = 35 V, 1H = 50 V, 1J = 63 V, 2A = 100 V, 2E = 250 V, 2G = 400 V, 2W = 450 V, 2J = 630 V and 3A = 1,000 V. Some makers use other letters for other voltages, so check the datasheet when a code is not in this list.

Ceramic dielectric codes (EIA-198)

• Class 1 (stable, for filters and oscillators): significant figure, multiplier and tolerance of the temperature coefficient. C0G (also called NP0) is 0 ± 30 ppm/K; U2J is 7.5 × −100 = −750 ± 120 ppm/K (N750); P2H is −150 ± 60 ppm/K.
• Class 2 (high capacitance, less stable): lowest temperature (X −55 °C, Y −30 °C, Z +10 °C), highest temperature (4 +65, 5 +85, 6 +105, 7 +125, 8 +150, 9 +200 °C) and the capacitance change over that range (P ±10%, R ±15%, S ±22%, T +22/−33%, U +22/−56%, V +22/−82%). X7R is −55 to +125 °C with ±15%; Y5V is −30 to +85 °C with +22/−82%.
• Class 2 capacitors also lose capacitance with DC voltage and with age, which the code does not show — the maker’s curves do.
• The IEC names are decoded too: NP0, N150 … N1500, P100, the IEC letters CG, PH, UJ and class 2 codes such as 2X1 (= X7R).

Film capacitor types (MKT, MKP …)

European makers such as WIMA mark film capacitors with type letters: M stands for metallized electrodes and F for film/foil construction. MKT and MKS are metallized polyester (PET), MKP metallized polypropylene (PP), MKC polycarbonate, MKN polyethylene naphthalate (PEN) and MKI polyphenylene sulfide (PPS); FKP and FKT (or KP and KT) are polypropylene and polyester film/foil types, KS polystyrene and MP metallized paper. Polypropylene types are the usual choice for snubbers, pulse duty and high-Q filters. Makers elsewhere often use their own letters.

Safety capacitors: X and Y

X1, X2 and X3 capacitors are made to sit across the mains (line to line or line to neutral); Y1 to Y4 capacitors go from line to protective earth, where a failure could cause an electric shock. Both are tested to fail safely under IEC 60384-14. Many parts carry two approvals, such as X1Y2 or X1/Y2. Replace them only with a capacitor of the same class and voltage rating.

Sources

• IEC 60062:2016+AMD1:2019, Marking codes for resistors and capacitors (RKM code, tolerance letters, two-character code)
• ANSI/EIA-198-1, Ceramic dielectric capacitors classes I, II, III and IV (temperature-characteristic codes)
• IEC 60384-1 (generic specification), IEC 60384-8/9 (class 1 and 2 ceramic codes) and IEC 60384-14 (X and Y safety capacitors)
• Manufacturer part-number conventions for rated-voltage codes (for example Panasonic, Nichicon, Murata, TDK)

Limitations

• Makers also print their own codes, logos and date codes. A group the calculator does not recognise is listed as such — look it up in the maker’s datasheet.
• Some groups are genuinely ambiguous (470 can be 47 pF by the code or 470 pF on older parts; 1V is 35 V as a code; 2R2 is 2.2 pF but also an IEC dielectric code; X2 on its own is a safety class but also a tiny-chip code). Every reading is shown; the part type and size usually decide.
• Electrolytic and tantalum capacitors have a polarity mark (a stripe, a + or a longer lead) that a text code cannot show. Fit them the right way round.
• The codes say nothing about leakage, ESR or lifetime, and class 2 ceramics lose much of their capacitance at their rated voltage. Check the datasheet for critical circuits.
• Date codes, logos and the makers’ own series names are not decoded (except the series number after a film type, such as MKS 2); they are listed as not recognised.

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