Resistors: types, values, colour codes and SMD codes
Resistor types (thick film, thin film, metal film, wirewound, shunt), E-series values, tolerance, power rating per package, colour code and SMD marking codes.
Types and where they are used
| Type | Typical tolerance | Use |
|---|---|---|
| Thick-film SMD | 1 % or 5 % | Almost everything on a modern board |
| Thin-film SMD | 0.1 % to 1 % | Precision dividers, sensor front-ends, low drift |
| Metal-film through-hole | 1 % | Breadboards, general purpose |
| Carbon-film through-hole | 5 % | Cheap, noisier; old designs |
| Wirewound | 1 % to 5 % | High power, not for high frequency |
| Current-sense shunt | 0.5 % to 1 % | Milliohm values for measuring current |
Standard values: the E-series
Resistors are not made in every value. They follow the E-series, where each value is a fixed step above the previous one. E12 (10 % steps): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82, then ×10. E24 adds values in between for 5 % parts; E96 has 96 values per decade for 1 % parts. When a calculation gives 260 Ω, you pick 270 Ω and check the result still works.
Colour code
Through-hole resistors use colour bands: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. Four-band parts: two digits, multiplier, tolerance (gold 5 %, silver 10 %). Five-band parts: three digits, multiplier, tolerance (brown 1 %). When in doubt, measure; that is faster than squinting.
SMD codes
SMD resistors in 0603 and larger may be printed. 3 digits: two digits and a multiplier, so 103 = 10 × 10³ = 10 kΩ. 4 digits: three digits and a multiplier, 1002 = 10.0 kΩ. R marks the decimal point: 4R7 = 4.7 Ω. 1 % parts often use the EIA-96 code (two digits for the value index plus a letter), such as 01C = 10 kΩ. 0402 parts carry no marking at all.
Power rating by size
| Package | Typical rating (thick film) |
|---|---|
| 0402 | 1/16 W (63 mW) |
| 0603 | 1/10 W (100 mW) |
| 0805 | 1/8 W (125 mW) |
| 1206 | 1/4 W (250 mW) |
| 2512 | 1 W (depends on series) |
Check the exact series datasheet: anti-surge and high-power variants exist in every size.
Choosing a resistor becomes engineering when tolerance, temperature drift, surge or voltage rating matter: current shunts, dividers for measurement, resistors on mains or high-voltage lines. Those choices are made and documented in our schematic phase.
Parts and tools to practise
| Item | What to look for | Buy |
|---|---|---|
| Resistor assortment, 1 % metal film | E24 or E12 values from 10 Ω to 1 MΩ, 1/4 W. Sorted in labelled bags or a box. | View on Amazon ↗ |
| SMD resistor and capacitor sample book | 0603 or 0805 values in a book. Handy for rework once you solder SMD. | View on Amazon ↗ |
| Digital multimeter | Auto-range with continuity beeper, CAT III rated. You will use it every day. | View on Amazon ↗ |
| Component tester | Identifies and measures resistors, capacitors, diodes and transistors automatically. | View on Amazon ↗ |
Links go to Amazon. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. We only list tools of the kind we use on our own bench.
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