Inductor Tolerance Codes: Absolute (±nH) vs Percentage (±%) Decoded

Walsin quotes inductor tolerance two incompatible ways: an absolute figure in nanohenries (±0.1 nH, ±0.2 nH, ±0.3 nH, ±0.5 nH) on 994 of 5,410 real parts, and a percentage (±2% up to ±30%) on 4,393 more. The two numbers are not on the same scale and cannot be compared by size alone — ±0.3 nH on a 5.6 nH part is a looser tolerance than ±5%. A numeric filter that strips the symbols and sorts on the bare number gets the ranking backwards.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, built this decode from the full inductor parametric export published by Walsin Technology (Walsin) — 5,411 rows, one of which (Test123999) is a QA test row excluded from every count below. The real total is 5,410 parts. Every part number in this post is real and checked against that extract.

What does an inductor tolerance of ±0.3 nH actually mean?

It means the part can sit ±0.3 nH away from its stated nanohenry value, not ±0.3%. On a 0.3 nH part that is a tolerance of 100% of nominal; on a 5.6 nH part in the same series it is 5.4%. The Tolerance column in Walsin’s export carries exactly 12 distinct values across the 5,410 real rows, and four of them are absolute nanohenry figures rather than percentages:

Tolerance value	Parts	System
±5%	1,475	Percentage
±2%	924	Percentage
±10%	754	Percentage
±25%	532	Percentage
±20%	462	Percentage
±0.1nH	389	Absolute
±0.2nH	355	Absolute
±0.3nH	218	Absolute
±3%	173	Percentage
±30%	73	Percentage
±0.5nH	32	Absolute
0 (literal integer)	23	Neither — see below

994 rows (18.4% of the catalogue) carry an absolute nanohenry tolerance. 4,393 (81.2%) carry a percentage. The remaining 23 carry a literal integer 0, which is a placeholder, not a specification — covered later in this post.

Which Walsin inductor series use absolute tolerance, and which use percentage?

Seven series, all small-signal multilayer or wirewound types, carry some absolute-tolerance rows: WLCM Series, MCI Series, MCI-TM, MCI Automotive Series, WCI Series, WCA Series and WQCM Series. None of the seven is exclusively absolute — every one of them also carries percentage-tolerance rows, at larger case sizes or higher inductance values within the same series name:

Series	Absolute rows	Percentage rows	Total
WLCM Series	369	190	559
MCI Series	333	168	501
MCI-TM	110	62	172
MCI Automotive Series	76	63	139
WCI Series	48	672	720
WCA Series	48	574	622
WQCM Series	10	16	26

The other 38 series in the catalogue (WLCW, WQCW, WLFW/WFI, AIP and the rest) carry percentage tolerance exclusively. Two more series — BIH and WTBL — carry neither; every row in both reads the literal 0 covered below. No series anywhere in the 47-series catalogue publishes absolute tolerance exclusively.

Exactly where does Walsin switch from nH to percent?

By case size first, then by inductance value within it. Absolute tolerance appears only at the three smallest case sizes — 0603(0201), 1005(0402) and 1608(0603) — and never above a nominal 6.2 nH anywhere in the 5,410-part catalogue. Every part at 6.8 nH or higher, in all 47 series, is a percentage tolerance.

At the smallest case size, 0603(0201), the handoff is not a clean cut. WLCM Series, MCI Series and MCI-TM each publish the same nominal inductance value under both systems as separate, real, orderable part numbers. At 5.6 nH in WLCM Series, 0603(0201), five real parts exist:

Part number	Tolerance	System	True relative tolerance	Match / mismatch
WLCM0603Z0B5N6TB	±0.1nH	Absolute	1.8%	Tightest of the five
WLCM0603TGH5N6TB	±3%	Percentage	3.0%	Second-tightest
WLCM0603Z0C5N6TB	±0.2nH	Absolute	3.6%	Third-tightest — mismatch: a naive parse of “0.2” ranks this ahead of ±3%, the true ordering has it behind
WLCM0603TGJ5N6TB	±5%	Percentage	5.0%	Fourth-tightest
WLCM0603Z0S5N6TB	±0.3nH	Absolute	5.4%	Loosest of all five — a naive parse of “0.3” ranks this as the tightest-looking value in the group

All five are 5.6 nH, same series, same case size. Ranked by the bare number in the Tolerance column (0.1, 0.2, 0.3, 3, 5), the three absolute parts look like the tightest group. Ranked by what the number actually means relative to the part’s own inductance, WLCM0603Z0S5N6TB (±0.3 nH) is the loosest of all five, looser than both percentage options.

At every case size larger than 0603(0201) — 1005(0402) and 1608(0603) — the same seven series hand off cleanly instead: no nominal inductance value is sold under both systems, and the boundary sits between 5.1–6.2 nH absolute and 5.6–6.8 nH percentage depending on the series. The 0603(0201) overlap is the exception, not the rule.

How is the tolerance letter encoded in a Walsin inductor part number?

As a single letter immediately before the inductance code, in the same position regardless of which system is in use. Across all seven absolute-tolerance series the same eight letters carry the same meaning on every part checked:

Letter	Meaning	System	Example	Inductance
B	±0.1 nH	Absolute	WLCM0603Z0B0N3TB	0.3 nH
C	±0.2 nH	Absolute	WLCM0603TGC0N3TB	0.3 nH
S	±0.3 nH	Absolute	WLCM0603Z0S0N3TB	0.3 nH
D	±0.5 nH	Absolute	WCA1005CP1N0D	1.0 nH
G	±2%	Percentage	WCA1005CP5N6G	5.6 nH
H	±3%	Percentage	MCI0603HQ6N8HHBP	6.8 nH
J	±5%	Percentage	WCA1005CP5N6J	5.6 nH
K	±10%	Percentage	WCA1005CP5N6K	5.6 nH

The letter alone tells you which system you are reading, but not the magnitude without also checking whether the row is absolute or percentage — B, C, S and D never appear on a percentage row and G, H, J, K never appear on an absolute row across the parts checked for this post, so the two alphabets do not collide with each other. They are simply read differently: a nanohenry figure for one group, a percent figure for the other.

What does a numeric filter do wrong when it reads both systems as one number?

It mis-ranks 1,017 of the 5,410 real parts — 18.8% of the catalogue — as carrying a tolerance of 1.0 or tighter. Strip the ± sign and the unit text from the Tolerance column and cast what is left to a number: every one of the 994 absolute rows reduces to 0.1, 0.2, 0.3 or 0.5, and the 23 literal-zero rows reduce to 0.0. All 1,017 then read as “1% or better,” tighter than the tightest real percentage part in the catalogue, which is ±2%.

None of that is true. The 994 absolute rows have a true relative tolerance that runs from 1.6% (MCI0603HQ6N2BHBP, 6.2 nH at ±0.1 nH, the tightest real part in the group) up to a full 100% (WLCM0603Z0S0N3TB, 0.3 nH at ±0.3 nH, the loosest). The 23 literal-zero rows have no tolerance value published at all — see the next question. A filter built on the bare number will return a 100%-tolerance part to a query for “tightest available inductor” and miss every genuinely tight ±2% part along the way.

Part number	Tolerance string	Naive numeric parse	True relative tolerance	Match / mismatch
MCI0603HQ6N2BHBP	±0.1nH	0.1	1.6%	Naive parse understates the true figure but both suggest “tight”
WLCM0603Z0S0N3TB	±0.3nH	0.3	100%	Mismatch — naive parse suggests tighter than ±2%; true figure is the loosest in the catalogue
WCA1005CP5N6G	±2%	2.0	2%	Match — this row genuinely is a percentage

Does a literal zero ever appear in the Tolerance column?

Yes, on 23 of the 5,410 real rows, split across two series. All 13 BIH Series rows carrying this defect are already on record in Venatech’s audit of the 208 no-datasheet parts. What has not been published before: all 10 WTBL Series rows carry the same literal integer 0 — not 0%, a bare zero that a spreadsheet reads as a valid numeric tolerance rather than a missing one. WTBL2012Z0U001PB is a real example: its Tolerance field reads 0, and its Inductance field also reads 0.0, while its Impedance (100MHz) column genuinely publishes 50 Ω. The row is not empty — several fields are real — but Tolerance and Inductance on every WTBL Series part are placeholders, not measurements.

A filter that treats this 0 as a tolerance claim would rank 23 real parts, across BIH and WTBL, as having zero tolerance — the tightest possible part in the entire catalogue. No real inductor has zero tolerance. Exclude both series from any tolerance-based sort, and request the real figure from Walsin before specifying either in a design where tolerance matters.

For how BIH and the other four no-datasheet series behave on their other published fields, see 208 Walsin inductors with no datasheet. For where tight tolerance is combined with a Q Min threshold for RF work, see choosing an RF matching inductor. Browse the full Walsin inductor range.

The short version

Walsin’s inductor Tolerance column carries 12 distinct values across two incompatible systems: 994 parts in nH, 4,393 in percent, and 23 as a literal zero that is not a tolerance at all. The nH system never appears above 6.2 nH and only at the three smallest case sizes; at 0603(0201), WLCM Series, MCI Series and MCI-TM even sell the same nominal value under both systems as separate part numbers. A numeric filter that strips the symbols and sorts on the bare number mis-ranks 1,017 parts, including one that looks like the tightest option in a result set and is in fact the loosest.

Send us your target inductance and tolerance and we will tell you which system the figure is in, and whether your case size carries both. Or give us one part number and we will decode it.

Already holding a part number? Paste it into the cross-reference tool — it reads the manufacturer from the number itself, returns the Walsin inductor candidates and states every field that differs rather than calling anything an alternative. Then check Hong Kong ready stock to see what is on the shelf today.

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Frequently asked questions

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