Chip resistors and capacitors are named by their body size. The four digits are the length and width in hundredths of an inch: 0805 is 0.08 in × 0.05 in.
Dimensions and typical resistor power ratings
| Package (imperial) | Size in mm | Typical thick-film resistor rating |
|---|---|---|
| 0402 | 1.0 × 0.5 | 1/16 W (0.063 W) |
| 0603 | 1.6 × 0.8 | 1/10 W (0.1 W) |
| 0805 | 2.0 × 1.25 | 1/8 W (0.125 W) |
| 1206 | 3.2 × 1.6 | 1/4 W (0.25 W) |
Power ratings vary between manufacturers and series, so treat these as typical and confirm on the datasheet.
Watch out for metric codes
The same package also has a metric code, in tenths of a millimetre: imperial 0603 is metric 1608, and imperial 0402 is metric 1005. The trap is that metric 0603 is imperial 0201 — a much smaller part. Most distributors and PCB tools in India use the imperial codes, and so does this store, but check which system a datasheet or footprint library is using.
Which size should you choose?
- 1206: easy to hand-solder and read. Good for higher power or higher voltage, and for boards where space is not a concern.
- 0805: the comfortable default for prototypes and hand assembly. Markings are still readable on resistors.
- 0603: the common choice for production boards. Hand-solderable with a fine tip and tweezers.
- 0402: for dense designs. Realistically needs solder paste and hot air or reflow; resistors usually carry no marking.
Things that change with size
- Power: a smaller resistor dissipates less. Calculate I² × R and leave margin.
- Voltage: smaller packages have lower maximum working voltage.
- Capacitance under DC bias: for the same value and voltage rating, a ceramic capacitor in a larger package generally keeps more of its capacitance when voltage is applied. See our MLCC dielectric guide.
- Parasitic inductance: smaller packages have less, which helps high-frequency decoupling.
Keep it consistent
Using one size for most passives on a board (for example, all 0603) simplifies assembly and stock. Step up to a larger size only where power, voltage or capacitance requires it.
Filter Resistors and Capacitors by package to see what is available in each size.