NEWS

Passive Component Case Sizes: Imperial and Metric, Every Line

Q: Do Walsin’s inductor size codes match the measured dimensions?

Not always. 497 inductors labelled metric 1005, nominally 1.00 × 0.50 mm, carry a measured figure of 1.19 × 0.64 mm. 386 labelled 1608 measure 1.8 × 1.12 mm. WQCW1005Z0J1N0TB and WLCW1005Z0J1N0TB share a size code, share 1.0 nH, and need different footprints.

An 0402 case size is 1.00 by 0.50 mm if the code is imperial, and 0.40 by 0.20 mm if it is
metric. Walsin Technology (Walsin) uses both conventions in one catalogue. Its chip resistor
export writes imperial 0402 as 0402(1005) and metric 0402 as 01005(0402), in the same column
of the same file. Read the parentheses before you order.

Every dimension below comes from the L, W and T columns of Walsin’s own parametric
exports, held by Venatech Limited, an authorised Walsin distributor in Hong Kong: 24,026 MLCC,
234,815 chip resistor, 93,914 thin film, 5,410 inductor, 457 RF and 379 varistor part numbers.

What is 0402 in mm?

Imperial 0402 is 1.00 mm long by 0.50 mm wide. Metric 0402, also written 01005 in imperial,
is 0.40 mm long by 0.20 mm wide. The two differ by a factor of 2.5 in length and 6.25 in
area. Walsin’s MLCC and chip resistor exports both hold parts at both sizes.

A 0402 MLCC such as MT15N0R5C500 carries L = 1.00 ± 0.05 mm and W = 0.50 ± 0.05 mm. The
ultra-small size, listed as 01R5, carries L = 0.40 ± 0.02 mm and W = 0.20 ± 0.02 mm on parts
such as RF02N0R2A160.

On the chip resistor side the same two sizes appear as 0402(1005) with 28,085 part numbers
and 01005(0402) with 755. WR01X10R0FDL is a 1/32 W general purpose part at the smaller of
the two.

Is 0402 imperial or metric?

Both, depending on the line. Walsin’s MLCC export uses bare imperial codes. Its chip resistor
and thin film exports use imperial(metric). Its inductor export uses metric(imperial) —
the reverse order. Its RF export uses bare metric with no parentheses at all.

That is four conventions in one catalogue, and the ordering reverses between two of them. A
chip resistor 1206(3216) and an inductor 3216(1206) are the same physical size written
back to front. Strip the parentheses, as any script does, and the two files disagree.

Walsin product line	Size convention	Example as written	Physical L × W
MLCC	Bare imperial	`0603`	1.60 × 0.80 mm
Chip resistor	`imperial(metric)`	`0603(1608)`	1.60 × 0.80 mm
Thin film	`imperial(metric)`	`0603(1608)`	1.60 × 0.80 mm
Inductor	`metric(imperial)` — reversed	`0603(0201)`	0.60 × 0.30 mm
RF / LTCC	Bare metric, no brackets	`1608`	1.60 × 0.80 mm
Varistor	Disc diameter in mm	`10mm`	10 mm disc
Antenna	Free-text L × W × H	`3.2mm x 1.6mm x 1.2mm`	as written
Disc capacitor	No size column at all	—	datasheet drawing only

How does Walsin write case sizes on each product line?

Six different ways across eight lines. The MLCC ultra-small size has two names in two Walsin
documents — 01005 in the application guide and 01R5 in the parametric export. The
varistor line abandons codes entirely and quotes a disc diameter. Disc capacitors publish no
dimensions at all.

The anomalies matter more than the general rule, because a script written for one line
silently mis-parses another. Three examples from the inductor export alone.

Anomaly	Real part number	What the Size field says	What the dimension column says	Match / mismatch
Separator typo	`WLBD3216K2U310TP`	`3216(1206)`	`3.2&1.6` — ampersand, not asterisk	Match on size, mismatch on format — 19 rows affected
Code contradicts dimension	`WQBD1608HCU600TH`	`1608(0603)` = 1.60 × 0.80 mm	`3.2&1.6` = 3.20 × 1.60 mm	Mismatch — factor of two
Raw millimetres in the code field	`WQQC0806Z0J5N5PB`	`1.346*1.829`	`1.346*1.829`	Mismatch — no code at all, 25 rows
Width exceeds length	`HCM1012GD500A05P`	`1012`	`1.0*1.25`	Mismatch — 1.0 mm long, 1.25 mm wide

Unique to Venatech’s data. In Walsin’s inductor export, 19 rows carry an ampersand in
place of the asterisk in the Size L*W (mm) field, 25 rows carry a raw millimetre
dimension in the Size field instead of a code, and one row — WQBD1608HCU600TH — has a
size code reading metric 1608 while its own dimension column reads 3.2 × 1.6 mm. Measured
across Walsin’s 5,410 real inductor part numbers; not published anywhere.

What is the full imperial and metric case size table?

Every case size Walsin’s exports actually return, ordered by physical length, with the code
each line uses and the part-number count behind it.

L × W (mm)	Imperial	Metric	MLCC	Chip resistor	Thin film	Inductor	RF / LTCC
0.40 × 0.20	01005	0402	`01R5` — 608	`01005(0402)` — 755	—	—	—
0.60 × 0.30	0201	0603	`0201` — 2,544	`0201(0603)` — 17,827	`0201(0603)` — 5,506	`0603(0201)` — 888	—
0.60 × 0.50	—	0605	—	—	—	—	`605` — 11
0.80 × 1.60	0306	0816	`0306` — 3	`0306(0816)` — 10	—	—	—
1.00 × 0.50	0402	1005	`0402` — 3,991	`0402(1005)` — 28,085	`0402(1005)` — 6,359	`1005(0402)` — 1,091	`1005` — 57
1.00 × 1.25	—	1012	—	—	—	`1012` — 7	—
1.10 × 0.90	—	1109	—	—	—	—	`1109` — 11
1.40 × 1.40	0505	—	`0505` — 97	—	—	—	—
1.40 × 1.10	—	1411	—	—	—	—	`1411` — 7
1.50 × 1.00	—	1510	—	—	—	—	`1510` — 1
1.60 × 0.80	0603	1608	`0603` — 4,730	`0603(1608)` — 42,374	`0603(1608)` — 7,562	`1608(0603)` — 962	`1608` — 161
1.60 × 3.20	0612	1632	—	`0612(1632)` — 1,725	—	—	—
1.80 × 1.40	—	1814	—	—	—	—	`1814` — 1
2.00 × 1.25	0805	2012	`0805` — 4,912	`0805(2012)` — 38,044	`0805(2012)` — 7,985	`2012(0805)` — 883	`2012` — 155
2.00 × 1.60	0806	2016	—	—	—	`2016(0806)` — 20	—
2.00 × 3.70	0815	2037	—	`0815(2037)` — 4	—	—	—
2.10 × 0.90	—	2109	—	—	—	—	`2109` — 1
2.50 × 2.00	1008	2520	—	—	—	`2520(1008)` — 664	`2520` — 28
2.50 × 5.00	1020	2550	—	`1020(2550)` — 878	—	—	—
2.79 × 2.79	1111	—	`1111` — 149	—	—	—	—
3.20 × 1.60	1206	3216	`1206` — 3,520	`1206(3216)` — 37,566	`1206(3216)` — 29,217	`3216(1206)` — 72	—
3.20 × 2.50	1210	3225	`1210` — 1,370	`1210(3225)` — 18,149	`1210(3225)` — 7,216	`3225(1210)` — 291	`3225` — 15
3.20 × 4.80	1218	3248	—	`1218(3248)` — 3,318	—	—	—
3.20 × 6.40	1225	3264 / 3263	—	`1225(3264)` — 1,708 · `1225(3263)` — 47	—	—	—
4.50 × 1.60	1806	4516	—	—	—	`4516(1806)` — 22	—
4.50 × 2.03	1808	—	`1808` — 419	—	—	—	—
4.50 × 3.20	1812	4532	`1812` — 1,020	—	—	`4532(1812)` — 104	—
4.60 × 6.30	1825	—	`1825` — 137	—	—	—	—
5.00 × 2.50	2010	5025	—	`2010(5025)` — 21,228	`2010(5025)` — 22,246	—	—
5.70 × 2.80	2211	—	`2211` — 57	—	—	—	—
5.70 × 5.00	2220	—	`2220` — 327	—	—	—	—
5.70 × 6.30	2225	—	`2225` — 141	—	—	—	—
6.40 × 3.20	2512	6432	—	`2512(6432)` — 22,154	`2512(6432)` — 7,823	—	—

Metric codes are quoted only where a Walsin export publishes one. A blank metric cell means
Walsin gives the imperial code alone for that size. Resistor arrays sit outside the scheme
entirely: Walsin writes them as element size and count — 0201*2 (194 parts), 0201*4 (194)
and 0602*8 (555).

Walsin’s inductor export also returns bare metric codes with no imperial companion, for larger
power parts: 4040, 4442, 5050, 5452, 5754, 6060, 7066, 7165 and 7265, plus
bare 2012, 2016, 2520, 3216 and 3225 alongside their bracketed forms.

Varistors use a different axis again. Walsin’s 379 varistor part numbers are grouped by disc
diameter — 5 mm (41 parts), 7 mm (41), 10 mm (53), 14 mm (53), 18 mm (20), 20 mm (49),
25 mm (21), 32 mm (19), 34 mm square (42), 40 mm (19) and 53 mm (21).

How thick is each case size?

Thickness is not fixed by the case code, and that is where most footprint and process mistakes
originate. Across Walsin’s MLCC extract a 1206 ranges from 0.80 mm to 1.60 mm and a 1210 from
0.85 mm to 2.50 mm. The code fixes two dimensions out of three.

MLCC case size	Nominal L × W (mm)	Thinnest in the extract	Thickest in the extract	Part numbers
`01R5`	0.40 × 0.20	0.20 mm	0.20 mm	608
`0201`	0.60 × 0.30	0.30 mm	0.30 mm	2,544
`0306`	0.80 × 1.60	0.50 mm	0.50 mm	3
`0402`	1.00 × 0.50	0.30 mm	0.50 mm	3,991
`0505`	1.40 × 1.40	1.15 mm	1.15 mm	97
`0603`	1.60 × 0.80	0.50 mm	0.80 mm	4,730
`0805`	2.00 × 1.25	0.60 mm	1.25 mm	4,912
`1111`	2.79 × 2.79	1.60 mm	1.78 mm	149
`1206`	3.20 × 1.60	0.80 mm	1.60 mm	3,520
`1210`	3.20 × 2.50	0.85 mm	2.50 mm	1,370
`1808`	4.50 × 2.03	1.25 mm	2.00 mm	419
`1812`	4.50 × 3.20	1.25 mm	3.10 mm	1,020
`1825`	4.60 × 6.30	1.60 mm	2.80 mm	137
`2211`	5.70 × 2.80	1.60 mm	2.80 mm	57
`2220`	5.70 × 5.00	1.60 mm	3.10 mm	327
`2225`	5.70 × 6.30	1.60 mm	2.80 mm	141

Walsin’s chip resistor and thin film exports publish no L, W or T columns at all. For
those two lines the case code is the only dimensional information in the parametric data, and
the drawing table in the datasheet is the only source for thickness.

Which case codes are reverse geometry or wide terminal?

Six of them, and they read as ordinary codes. 0306, 0612, 0815, 1020, 1218 and 1225
are wider than they are long — the terminations sit on the long sides. An 0603 footprint will
not take an 0306.

Code as written	Line	L × W (mm)	Why the geometry inverts	Real part number
`0306`	MLCC	0.80 × 1.60	Reverse geometry, shortened current path	`0306B225J4R0`
`0306(0816)`	Chip resistor	0.80 × 1.60	Reverse geometry, low-ohm current sense	`WW06YR001FTL`
`0612(1632)`	Chip resistor	1.60 × 3.20	Wide terminal, heat out through the pads	`WW12YR0L5FTL`
`0815(2037)`	Chip resistor	2.00 × 3.70	Wide terminal, low-ohm current sense	`WW15WR005FTL`
`1020(2550)`	Chip resistor	2.50 × 5.00	Wide terminal power	`WK20L1R00FTL`
`1218(3248)`	Chip resistor	3.20 × 4.80	Wide terminal power	`MR18W1R00FTL`
`1225(3264)`	Chip resistor	3.20 × 6.40	Wide terminal power	`WK25L1R00FTL`
`1225(3263)`	Chip resistor	3.20 × 6.30	Same imperial code, metric written 3263	`WW25YR0L5FTL`

Two MLCC sizes are also wider than long without being called reverse geometry: 1825 measures
4.60 by 6.30 mm and 2225 measures 5.70 by 6.30 mm, as on 2225B103J102.

Where do the conventions collide?

On three digit strings. 0402, 0603 and 1206 each appear in Walsin’s own size fields with
two different physical meanings, depending on which line’s file you opened and whether the
number sits inside or outside the parentheses.

Digit string	Where it appears	What it means there	Match / mismatch
`0402`	MLCC `Size` = `0402`	1.00 × 0.50 mm (imperial)	—
`0402`	Chip resistor `0402(1005)`	1.00 × 0.50 mm (imperial)	Match with MLCC
`0402`	Chip resistor `01005(0402)`	0.40 × 0.20 mm (metric)	Mismatch — 2.5× shorter
`0402`	Inductor `1005(0402)`	1.00 × 0.50 mm (imperial, in brackets)	Match with MLCC
`0603`	MLCC `Size` = `0603`	1.60 × 0.80 mm (imperial)	—
`0603`	Chip resistor `0603(1608)`	1.60 × 0.80 mm (imperial)	Match with MLCC
`0603`	Inductor `Size` = `0603(0201)`	0.60 × 0.30 mm (metric)	Mismatch — 2.67× shorter
`1206`	Chip resistor `1206(3216)`	3.20 × 1.60 mm (imperial)	—
`1206`	Inductor `3216(1206)`	3.20 × 1.60 mm (imperial, in brackets)	Match, digits reversed

Unique to Venatech’s data. Walsin’s chip resistor export contains 28,085 parts whose
Size field begins 0402 and means 1.00 × 0.50 mm, and 755 parts whose Size field ends
(0402) and means 0.40 × 0.20 mm. Same column, same file. Meanwhile the inductor export
writes 3.20 × 1.60 mm as 3216(1206) while the chip resistor export writes the identical
size as 1206(3216). An engineer who assumes one convention and reads the other orders a
part with the wrong footprint.

The inductor export adds a second layer, because the size code is nominal and the dimension
column is measured. 497 inductors labelled metric 1005 carry a measured Size L*W (mm) of
1.19 × 0.64 mm. 386 labelled 1608 measure 1.8 × 1.12 mm. 561 labelled 2012 measure
2.29 × 1.73 mm.

Inductor size code	Real part number	Nominal from the code	Measured in the export	Match / mismatch
`1005(0402)`	`WLCW1005Z0J1N0TB`	1.00 × 0.50 mm	1.0*0.5	Match
`1005(0402)`	`WQCW1005Z0J1N0TB`	1.00 × 0.50 mm	1.19*0.64	Mismatch — 19% longer, 28% wider
`1608(0603)`	`WLCW1608Z0J1N6PB`	1.60 × 0.80 mm	1.6*0.8	Match
`1608(0603)`	`WQCW1608Z0J1N6PB`	1.60 × 0.80 mm	1.8*1.12	Mismatch — 40% wider
`2012(0805)`	`WLCW2012Z0J2N2PB`	2.00 × 1.20 mm	2.29*1.73	Mismatch — 44% wider
`0603(0201)`	`WLCM0603Z0B0N3TB`	0.60 × 0.30 mm	0.6*0.3	Match
`1608(0603)`	`WQBD1608HCU600TH`	1.60 × 0.80 mm	3.2&1.6	Mismatch — twice the length
`1012`	`HCM1012GD500A05P`	1.00 × 1.20 mm	1.0*1.25	Mismatch — wider than long

Those pairs share an inductance and a size code, and need different footprints. The WLCW and
WQCW prefixes are the only warning.

The pattern repeats at larger sizes. Of the 664 inductors coded 2520(1008), only 22 measure
2.5 × 2.0 mm; 523 measure 2.92 × 2.79 mm. Of the 104 coded 4532(1812), only 22 measure
4.5 × 3.2 mm. All 20 coded 2016(0806) measure 1.8 × 1.12 mm rather than 2.0 × 1.6 mm. On this
line the code is a family name, not a dimension.

How do I stop ordering the wrong case size?

Never quote a bare four-digit code. Quote the millimetre dimensions alongside it, and on
inductors quote the measured Size L*W figure rather than the code. If a supplier or a
datasheet gives only the code, ask which convention it is in before releasing the footprint.

Three habits catch almost everything. Check the third dimension, because thickness is not in
the code. Check whether width exceeds length, because six Walsin resistor codes and two MLCC
codes are wider than they are long. And check the measured dimension column where one exists,
because on Walsin’s inductor line the code is nominal and the measurement is not.

FAQ

What is 0402 case size in mm?

Imperial 0402 is 1.00 mm long by 0.50 mm wide. Metric 0402 is 0.40 mm long by 0.20 mm wide and is written 01005 in imperial. Walsin’s chip resistor export holds 28,085 parts at the first and 755 at the second, in the same Size column of the same file.

What is 0603 case size in mm?

Imperial 0603 is 1.60 mm long by 0.80 mm wide. Metric 0603 is 0.60 mm long by 0.30 mm wide, which is imperial 0201. Walsin’s MLCC export writes the larger part as 0603, while its inductor export writes the smaller part as 0603(0201). Same four digits, 2.67 times the length apart.

Is a chip case size code imperial or metric?

It depends on the product line. Walsin’s MLCC export uses bare imperial. Its chip resistor and thin film exports use imperial(metric). Its inductor export uses metric(imperial), the reverse order. Its RF export uses bare metric with no brackets. Four conventions in one manufacturer’s catalogue.

Does the case size code tell me the thickness?

No. Across Walsin’s MLCC extract a 1206 runs from 0.80 mm to 1.60 mm thick and a 1210 from 0.85 mm to 2.50 mm. The code fixes length and width only. Walsin’s chip resistor and thin film exports publish no thickness column at all, so the datasheet drawing is the only source.

What is a reverse geometry chip resistor?

One whose terminations sit on the long sides, so width exceeds length. Walsin writes the 0.80 × 1.60 mm size as 0306 on MLCC and 0306(0816) on chip resistors. WW06YR001FTL is a real 1 mΩ current sense part at that size. It cannot use an 0603 footprint.

Why does Walsin list 1225 as both 3264 and 3263?

Two different series share the imperial code and Walsin writes the metric companion differently for each. The thick film wide terminal power group uses 1225(3264) on 1,708 parts, and the metal foil low-ohm sensing group uses 1225(3263) on 47 parts, including WW25YR0L5FTL. A string filter on one silently drops the other.

What does 01005 mean, and why does Walsin call it 01R5?

01005 is the imperial code for a 0.40 × 0.20 mm chip, metric 0402. Walsin’s MLCC application guide calls the size 01005 and its parametric export calls it 01R5 — same parts, two names in two Walsin documents. The export holds 608 MLCC part numbers at that size, such as RF02N0R2A160.

Do Walsin’s inductor size codes match the measured dimensions?

Not always. 497 inductors labelled metric 1005, nominally 1.00 × 0.50 mm, carry a measured figure of 1.19 × 0.64 mm. 386 labelled 1608 measure 1.8 × 1.12 mm. WQCW1005Z0J1N0TB and WLCW1005Z0J1N0TB share a size code, share 1.0 nH, and need different footprints.

Next step

Case size questions are cheapest to settle before the footprint is released. Send the BOM
lines and Venatech Limited, an authorised Walsin distributor in Hong Kong, will return the
Walsin size code in the convention that line uses, the measured length, width and thickness
where Walsin publishes them, and whether the part is reverse geometry or wide terminal.

Send your BOM to Venatech · Browse the
Walsin inductor range · Read
Chip resistor power rating by case size and
Wide terminal power resistors: 1225, 1020 and 0612.

Cross it yourself. The cross-reference tool takes a single part number or a whole BOM column and returns the Walsin candidates with every field that differs stated plainly — qualification stays with you. Ready stock shows what is held in Hong Kong today, with an RFQ against any line.