Tolerance Code Letters: 11 Letters Are Shared by Walsin Capacitor and Resistor Part Numbers, and 6 of Them Change Meaning

The same tolerance code letters are printed on capacitor and resistor part numbers, and six of them do not mean the same thing. We read the tolerance letter on 354,041 Walsin part numbers across five families: 11 letters appear in more than one family, and 88,209 part numbers carry one of the 6 that change meaning.

A decoder keyed on the letter alone returns a correct number and a wrong unit, and that is the failure that survives a spot check, because the digits look right. Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the parametric export files published by Walsin Technology (Walsin) for MLCC, chip resistor, thin film, disc capacitor and varistor. This post is written from the tolerance letter inside each part number, read at its fixed position and set against the Tolerance column of the same row in 00_ALL_MLCC_parts_combined.xlsx, the 64 non-empty chip resistor files, the thin film files, Walsin_DiscCap_ALL.xlsx and Walsin_MOV_ALL.xlsx. Every part number below is real. We will not tell you what a letter means in a family we have not counted. We will show you where it flips.

Which tolerance letters appear in more than one Walsin product family?

Eleven. We took the tolerance letter at its position in every part number of five families, 354,041 rows in all, and listed which letters occur in more than one. The shared letters are A, B, C, D, F, G, J, K, M, P and Z; five of them mean the same thing everywhere they appear and six do not. The inductor export is left out here because its tolerance letters sit at a different position and are covered in inductor tolerance codes.

The letter sits at a different character position in each family: the ninth character on MLCC and disc capacitors, the tenth on chip resistors and thin film, and the sixth on varistors. Each cell below is the value in the Tolerance column on the rows carrying that letter, with the row count.

We have not seen this counted anywhere. 88,209 of the 354,041 part numbers, 24.9 percent, carry A, B, C, D, P or Z, the six letters whose meaning depends on the family. The five stable letters F, G, J, K and M carry 210,710 rows. The remaining 55,122 carry a letter that appears in one family only: T, W, X, Y, Q and V.

Which four letters carry the same number in picofarads on a capacitor and in percent on a resistor?

A, B, C and D. On a Walsin MLCC they mean ±0.05, ±0.1, ±0.25 and ±0.5 pF; on a thin film resistor the same four letters mean ±0.05, ±0.1, ±0.25 and ±0.5 percent. The digits are identical, and the unit changes from an absolute capacitance to a relative fraction, so a parser that stores the number and guesses the unit is wrong on 87,293 part numbers carrying A, B, C or D. That is the sum of the four rows above.

The error grows when you convert both to what they mean for the part. We worked three pairs through. On MT15N1R0B500 the letter B is ±0.1 pF on a 1.0 pF part, which is ±10 percent. On WF25H1R00BTL the same letter B is ±0.1 percent on a 1.00 ohm part, ±0.001 ohm.

For the full capacitor letter table, see tolerance, TCR and dielectric codes decoded. The point here is narrower: the table is a different table in each family, and the letter is a key into whichever one you are standing in.

What do P and Z mean when you read them across families?

P and Z each take a different value in every family that uses them. P is ±0.02 pF on 53 MLCC rows and a jumper with no tolerance on 126 chip resistor rows; Z is −20/+80 percent on 15 MLCC rows, +80/−20 percent on 46 disc capacitor rows and 0/−10 percent on 676 chip resistor rows. Two of the three Z readings are the same band written in opposite order.

UF15N0R2P500 carries P as a 0.02 pF tolerance on a 0.2 pF part. WF04A000 PTL carries P as the jumper marker on a 0 ohm part, where no tolerance exists to decode. 1206F474Z500 is a 470 nF MLCC whose Z reads −20/+80 percent, and YV500102Z040 is a 1000 pF disc capacitor whose Z reads +80/−20 percent. WF20M1R0 ZTL is a trimmable chip resistor whose Z reads 0/−10 percent. So one letter reads as a wide band skewed positive on the capacitor side and as a one-sided negative band on the resistor side.

Which letters can a decoder read without knowing the family?

F, G, J, K and M, and only inside this catalogue. Across 210,710 part numbers these five letters carry ±1, ±2, ±5, ±10 and ±20 percent in every family that uses them. F is used by three families, J and M by three, K by four, and G by two. A decoder can read these without a family check and be right.

Those five are not the whole truth about those columns. The letter is the intention; the column is what the export states, and we found rows where they disagree. On MLCC, J sits on 5,723 rows but only 5,495 state ±5 percent in the plain form, and 220 state a bare -0.05 from the known MG-series defect. For that and the MG termination column, see the MLCC termination column that holds tolerances. The five stable letters are stable in meaning, not in the cell beside them.

Does one tolerance ever have two letters inside one series?

Yes, once that we found: ±1 percent is written F and W inside the same thin film series. The Tantalum nitride MF series states ±1 percent on 4,089 rows with the letter F and on 15 rows with the letter W, for example MF12W1012WTL, and no other thin film series uses W. A decoder with a one-letter table for ±1 percent reads 15 parts as unknown.

The letter T is the opposite case, one letter standing for a value no other family shares. T is ±0.01 percent on all 52,808 rows of the WF precision thin film series and is not a tolerance letter in any other family. The chip resistor letters X, Y and Z are three asymmetric bands, 0/−30, 0/−20 and 0/−10 percent, on 1,135, 1,129 and 676 rows of the Thick Film Trimmable series. A table that lists only the symmetric letters leaves 2,940 chip resistor rows unread.

What should a decoder key on before it reads the letter?

The family, then the position, then the letter. That is how our free cross-reference tool handles it: the unit comes from the family and the digits come from the letter, and any disagreement with the Tolerance column is stated, not smoothed over. Three rules, each measured above:

1. Never store the digits and guess the unit. A, B, C and D flip it on 87,293 part numbers.
2. Treat P and Z as family-specific. Each takes three values or two across the families that use it.
3. Do not carry a letter table from another manufacturer into this one. Fill the incumbent column from your own datasheet: other makers print their own tolerance legends, and we do not reproduce them. Confirm against both datasheets and qualify in your own circuit.

We hold 28 Walsin datasheets, 451 pages, covering 26 MLCC and 2 chip resistor series, and we checked the WR and MR chip resistor sheets for their tolerance legend. We hold none for thin film, disc capacitor or varistor, so the letters for those three are read from the export alone and should be confirmed on Walsin’s own site. What is in Hong Kong is on ready stock, 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The capacitor range sits on the MLCC page. Our UL file is E182369, and you can look it up yourself.

The short version

Eleven tolerance letters are shared between Walsin capacitor and resistor part numbers. F, G, J, K and M mean the same everywhere. A, B, C and D keep their digits and change their unit between pF and percent, P changes from a tolerance to a jumper marker, and Z takes three bands. 88,209 of 354,041 part numbers, 24.9 percent, carry a letter that depends on the family. Inside the MF thin film series, ±1 percent has two letters. We will not tell you a letter means a tolerance. We will show you the family it has to be read in.

Send us the tolerance letter your parser extracts and the family it came from, and we will tell you which table it should have used. And a question back: when your script read a 0.5 off a part number, did it know whether that was picofarads or percent?

Frequently asked questions