Chip resistors and capacitors are named by their size, and two naming systems are in use: imperial codes in hundredths of an inch and metric codes in tenths of a millimetre. Parts lists, datasheets and suppliers mix them freely. The trap is that some codes exist in both systems with different meanings — an "0603" can be a 1.6 mm part or a 0.6 mm part. This converter shows both readings and the full size table.
How to use it
- Type the package code from the schematic, the part number or the parts list.
- Leave Detect selected, or choose the system if you know it.
- Read the matching code in the other system, the size and the typical power rating for a resistor of that size.
If the code exists in both systems, the result explains both possibilities.
The size table
The table under the result lists every common size from 008004 (0201 metric) to 2512 (6332 metric), with the current code highlighted. On laptop motherboards, 0201 and 0402 dominate; 0603 and 0805 appear in power circuits; 1206 and larger mostly carry current-sense resistors and fuses.
The 0603 and 0402 trap
- Imperial 0603 is 1.6 × 0.8 mm (metric 1608).
- Metric 0603 is 0.6 × 0.3 mm (imperial 0201).
The same applies to 0402: imperial 0402 is 1.0 × 0.5 mm, metric 0402 is imperial 01005. Ordering the wrong one gives you parts four times larger or smaller than the pads. Check the dimensions in millimetres before ordering, especially from datasheets written in metric.
Worked example
A schematic lists a capacitor as "C0603". The board is a modern laptop where nearly everything is tiny, and the pad measures about 0.6 mm across. That is metric 0603 — imperial 0201. Buying imperial 0603 parts would leave you with capacitors far too big for the pads. Choosing a package also matters for power, which Resistor Power and Package Rating Calculator checks; soldering technique for small parts is covered in Hot Air Station Basics for Laptop Repair.
FAQ
Which system do laptop schematics use?
Both appear. Many schematics use imperial codes in the footprint name; some ODMs use metric. When in doubt, measure the pads.
Is a larger package always better for a replacement?
Only if it fits. Larger parts handle more power and voltage, but must sit on the existing pads without bridging.
Are the power ratings exact?
They are typical values for thick-film resistors. Check the datasheet of the exact series.