Chip resistor power rating rises with case size, but it is not one value per size.
Walsin Technology (Walsin) rates 01005 at 1/32 W, 0201 at 1/20 W, 0402 at 1/16 W or
1/10 W, 0603 at 1/10 W or 1/8 W, 0805 at 1/8 W or 1/4 W, and 2512 at 1 W or 2 W.
What is the power rating of a 0603 chip resistor?
Most commonly 1/10 W. A higher-rated 1/8 W 0603 also exists, in far smaller numbers. Our
extract of Walsin’s general purpose chip resistor catalogue holds 8,582 parts at 0603 rated
1/10 W and 969 at 0603 rated 1/8 W. The footprint is identical. The construction is not.
Case size sets the ceiling. The series sets the actual rating. A thermal calculation
landing between 1/10 W and 1/8 W does not force you up a case size — but you have to name
the right series, and the higher-rated variant is a much shallower catalogue.
Does every resistor in one case size have the same power rating?
No. Seven of the ten case sizes in Walsin’s general purpose catalogue carry two or more
distinct power ratings. Only 01005, 0201 and 1218 are single-valued. Selecting by case size
alone and assuming a wattage is the most common cause of a thermally undersized BOM line.
Here is the full power-by-size matrix from our extract. Each cell is the number of real
parts we hold at that size and rating.
| Case size | 1/32 W | 1/20 W | 1/16 W | 1/10 W | 1/8 W | 1/4 W | 1/3 W | 1/2 W | 3/4 W | 1 W | 2 W |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 01005 (0402) | 755 | — | — | — | — | — | — | — | — | — | — |
| 0201 (0603) | — | 14,535 | — | — | — | — | — | — | — | — | — |
| 0402 (1005) | — | — | 6,783 | 2,768 | — | — | — | — | — | — | — |
| 0603 (1608) | — | — | — | 8,582 | 969 | — | — | — | — | — | — |
| 0805 (2012) | — | — | — | — | 7,613 | 1,938 | — | — | — | — | — |
| 1206 (3216) | — | — | — | — | — | 9,691 | — | 140 | — | — | — |
| 1210 (3225) | — | — | — | — | — | — | 1,799 | 4,960 | — | — | — |
| 1218 (3248) | — | — | — | — | — | — | — | — | — | 2,907 | — |
| 2010 (5025) | — | — | — | — | — | — | — | 1,938 | 4,016 | 140 | — |
| 2512 (6432) | — | — | — | — | — | — | — | — | — | 5,954 | 140 |
Three things in that matrix are worth stopping on.
0201 is enormous. 14,535 parts at a single rating of 1/20 W — the deepest single
size-and-power combination in the general purpose catalogue.
1210 does not overlap with 1206 the way most engineers expect. 1206 runs 1/4 W with a
thin 140-part 1/2 W line. 1210 runs 1/3 W and 1/2 W, with no 1/4 W at all. Going from 1206
to 1210 is not a like-for-like step up.
Some combinations exist but barely. 1206 at 1/2 W, 2010 at 1 W and 2512 at 2 W are all
140-part lines. Real options, but your resistance and tolerance may not be in them.
Datasheets, held locally:
_Walsin_Datasheets/Resistor/Walsin_WR_General_Purpose_Chip_Resistor.pdf and
_Walsin_Datasheets/Resistor/Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf. Walsin’s
public resistor product index is at https://www.passivecomponent.com/products/resistors/
— an index page, not a direct link to either PDF.
A real ladder, one part per case size
These are actual Walsin part numbers from our catalogue extract, one per case size. The
reference is the 0805 part. The right-hand column states field by field what matches and
what does not — this is a comparison of real parts, not a claim that any of them
substitutes for another.
| Walsin part number | Series | Case size | Resistance | Tolerance | TCR (ppm/°C) | Rated power | Match / mismatch vs WR08W1R00FTL |
|---|---|---|---|---|---|---|---|
| WR08W1R00FTL | Thick Film General Purpose | 0805 (2012) | 1.00 Ω | ±1% | −200 to +400 | 1/8 W | reference part |
| WR04W1R00FTL | Thick Film General Purpose | 0402 (1005) | 1.00 Ω | ±1% | −200 to +400 | 1/16 W | match: series, resistance, tolerance, TCR, Sn-base lead-free termination · mismatch: 0402 footprint, half the rated power |
| SR06W1R00FTL | Thick Film High Grade Anti-Sulfuration (Automotive) | 0603 (1608) | 1.00 Ω | ±1% | −200 to +400 | 1/10 W | match: resistance, tolerance, TCR, termination · mismatch: SR anti-sulfuration automotive series not WR general purpose, 0603 footprint, 1/10 W |
| WR01X10R0FDL | Thick Film General Purpose | 01005 (0402) | 10.0 Ω | ±1% | ≤ ±300 | 1/32 W | match: series, tolerance, termination · mismatch: 01005 footprint, 10.0 Ω not 1.00 Ω, symmetric ±300 TCR spec, 1/32 W |
| MR12X000 PTL | Thick Film General Purpose (Automotive) | 1206 (3216) | 0 Ω | jumper | not specified | 1/4 W | match: Sn-base lead-free termination only · mismatch: MR automotive series, 1206 footprint, 0 Ω jumper with no tolerance or TCR, 1/4 W |
| MR25X000 PTL | Thick Film General Purpose (Automotive) | 2512 (6432) | 0 Ω | jumper | not specified | 1 W | match: Sn-base lead-free termination only · mismatch: MR automotive series, 2512 footprint, 0 Ω jumper, 1 W |
How much should I derate a chip resistor’s power rating?
The rated power applies only up to a stated ambient temperature, then falls linearly to
zero at the maximum operating temperature. Thick film chip resistors conventionally hold
full rated power to +70 °C and derate to zero at +155 °C. Read your actual curve from the
series datasheet rather than assuming the convention.
Ambient is not room temperature. It is the air immediately around the resistor inside a
closed enclosure. A part beside a regulator can easily see +85 °C, at which point a derated
1/10 W part is delivering well under its nameplate. Two more factors are routinely missed:
pad size and copper pour change the thermal path, so the datasheet rating assumes a
specific test board, and pulse loading is a separate specification with its own curve.
What case size do I need for 1 W?
1218, 2010 or 2512. Our extract holds 2,907 general purpose parts at 1218 rated 1 W, 5,954
at 2512 rated 1 W, and a narrow 140-part line at 2010. Above 1 W, 2512 at 2 W is the only
general purpose thick film option, and it is also a 140-part line.
The choice between 1218 and 2512 at 1 W is rarely about power. The two outlines are
different shapes, so pad layout usually decides it. 2512 is the deeper catalogue at 1 W:
5,954 parts against 2,907 at 1218. If your requirement sits between 1 W and 2 W, read the
section below on the missing filter entries before concluding the catalogue cannot serve
you.
What is the rated power of a 0 Ω jumper?
It is a current rating problem disguised as a power rating. Walsin’s 0 Ω automotive jumpers
carry the same power figure as the resistive parts in that case size: MR02X000 PAL at
0201 is 1/20 W, MR12X000 PTL at 1206 is 1/4 W, MR10X000 PTL at 1210 is 1/2 W,
MR20X000 PTL at 2010 is 3/4 W and MR25X000 PTL at 2512 is 1 W.
For a jumper the governing limit is maximum current, not dissipation, because the
resistance is a maximum rather than a nominal. Take the current rating from the datasheet.
Why can I not find a 1.5 W chip resistor on Walsin’s search?
Because the value is not in the filter dropdown. Walsin’s public parametric search does not
offer 1.5 W or 1/5 W as selectable rated power options, yet both ratings exist as real
parts. Anyone checking the public search for a 1.5 W chip resistor concludes, incorrectly,
that Walsin does not make one.
The counts we hold are 1,950 parts at 1.5 W and 1,665 parts at 1/5 W — 3,615 real chip
resistors invisible to the public filter. If you have been stepping up a case size because
the search returned nothing at 1.5 W, the part you wanted may already exist.
Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the underlying
parametric data including these two ratings. Walsin’s export also fails above roughly
10,000 rows, which is why large resistor series must be pulled in slices — and why gaps
like this appear at all.
The checklist
Run these eight checks before a chip resistor goes onto a BOM.
- Compute worst-case dissipation, not nominal — maximum supply, minimum resistance
after tolerance and TCR, longest duty cycle. - Establish the real ambient at the resistor’s location inside the enclosure.
- Apply the derating curve from the actual series datasheet at that ambient.
- Check the rating exists in your chosen case size. Seven of ten sizes carry more than
one rating, and several combinations hold only 140 parts. - Confirm your resistance and tolerance exist at that rating. A 140-part line may not
carry your value. - Check pulse loading separately. Continuous power rating does not cover switched,
inrush or ESD-adjacent loads. - Check the series, not just the size. WR is general purpose, MR is automotive, SR is
high-grade anti-sulfuration automotive. They are not interchangeable by footprint. - Verify the orderable part number format, including any packaging suffix, before the
line goes to purchasing.
Frequently asked questions
What is the power rating of an 0805 chip resistor?
Either 1/8 W or 1/4 W, depending on the series. Our extract holds 7,613 Walsin general purpose parts at 0805 rated 1/8 W and 1,938 at 0805 rated 1/4 W. The footprint is the same. Confirm the rating from the specific part number rather than the case size.
Can I fit a 1206 resistor on an 0805 footprint to get more power?
No. The pads will not match and the solder joint will be unreliable. If you need more dissipation in the same outline, look for a higher-rated part in the same case size first. Walsin’s 1206 offers 1/4 W and 1/2 W; 0805 offers 1/8 W and 1/4 W.
Why is 0201 the largest group in the catalogue?
Because it is the workhorse size for dense consumer and mobile boards. Our extract holds 14,535 general purpose parts at 0201, all rated 1/20 W. It is the deepest single size-and-power combination in the general purpose data we hold.
What is the difference between the WR, MR and SR series?
WR is the general purpose thick film chip resistor. MR is the automotive thick film chip resistor. SR is the high-grade anti-sulfuration thick film chip resistor, also automotive. They differ in qualification and sulfur resistance, not only in power rating.
Are the 1.5 W and 1/5 W parts really available?
They exist in the catalogue data we hold. They are simply absent from Walsin’s public filter dropdown. Send the resistance, tolerance and case size you need and Venatech will check current availability rather than quote a stock figure that will be stale.
Next step
Send us the dissipation, ambient and case size constraint for each resistor line. We will
return the Walsin candidates with rated power, TCR, tolerance and series stated field by
field, including the 1.5 W and 1/5 W options that Walsin’s own search will not show you. We
will not tell you a part is equivalent. We will show you where it differs.
Send us your BOM → ·
Browse Walsin chip resistors →
Related reading: Low-ohm current sense resistors: thick film vs metal ·
Anti-surge chip resistors
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.