IDB-RCV-045
Electronics · E-series · color codes · dielectrics
Resistor & capacitor values & codes
Reading and choosing passives — the E-series preferred values, resistor colour and SMD codes, capacitor codes and dielectrics, and the derating that keeps them in spec.
Abstract
Passives only come in standard (E-series) values, and they're marked with compact codes. This reference decodes resistor colour bands and SMD codes, capacitor codes and dielectric types, and gives the derating rules that keep a chosen part actually meeting its number in circuit.
Section 1 is the E-series. Section 2 is resistor codes. Section 3 is capacitor codes and dielectrics. Section 4 is tolerance and selection. Section 5 is power and voltage derating. Section 6 is a quick reference.
1.The E-series (preferred values)
Components are made only in preferred values spaced logarithmically so each value's tolerance band just meets the next. Pick the nearest E-series value to your calculated one:
| Series | Tolerance | Values per decade |
|---|---|---|
| E6 | ±20% | 6 |
| E12 | ±10% | 12 |
| E24 | ±5% | 24 |
| E48 | ±2% | 48 |
| E96 | ±1% | 96 |
E12 (the everyday set): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 (× any decade). For tight dividers/filters use E96 (1%).
2.Resistor codes
4-band colour: digit · digit · multiplier · tolerance. 5-band adds a third digit (for 1%).
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | — |
| Grey / White | 8 / 9 | — | — |
| Gold / Silver | — | ×0.1 / ×0.01 | ±5% / ±10% |
SMD codes: 3-digit 472 = 47 × 10² = 4.7 kΩ; 4-digit 4702 = 470 × 10² = 47 kΩ; R marks the decimal: 4R7 = 4.7 Ω. EIA-96 uses 2 digits (a value lookup) + a letter (multiplier) for 1% parts.
3.Capacitor codes and dielectrics
Code is in pF: 3 digits = first two digits × 10^(third). 104 = 10 × 10⁴ pF = 100 000 pF = 100 nF. 220 = 22 pF. An R marks a decimal (4R7 = 4.7 pF). A trailing letter is tolerance.
Always note the voltage rating and the dielectric — the dielectric dominates real-world behaviour:
| Dielectric | Stability | Use |
|---|---|---|
| C0G / NP0 (class 1) | excellent, no DC-bias loss | timing, filters, RF; small values only |
| X7R (class 2) | ±15% over −55…+125 °C; loses C with DC bias | general decoupling, bulk |
| X5R | like X7R but to +85 °C | space-constrained decoupling |
| Y5V / Z5U | huge capacitance, terrible stability | last resort bulk only |
| Film | very stable, low loss | audio, snubbers, timing (bulky) |
| Aluminium electrolytic | high bulk C, polarised | power-rail bulk, low cost |
| Tantalum / polymer | high C small size, polarised | compact bulk — derate voltage hard |
4.Tolerance and selection
- Pick the nearest E-series value for the tolerance you need; don't specify a value that isn't made.
- MLCC DC bias: class-2 ceramics (X7R/X5R) lose capacitance under applied voltagesometimes 50–80% at rated volts. Choose a higher-voltage / larger case part and verify the effective capacitance at your operating voltage.
- Temperature coefficient: use C0G/NP0 where the value must be stable (oscillators, filters).
5.Power and voltage derating
Resistor power by SMD size (rated; derate to ~50%):
| Size | Rated power |
|---|---|
| 0201 | 1/20 W |
| 0402 | 1/16 W |
| 0603 | 1/10 W |
| 0805 | 1/8 W |
| 1206 | 1/4 W |
| 2010 / 2512 | 3/4 W / 1 W |
Capacitor voltage derating: MLCC to ~50–70% of rated (and watch DC bias); aluminium electrolytic to ~80%; tantalum to ~50% (lower in high-inrush rails) — tantalum fails short and can ignite if not derated.
6.Quick reference
- E12: 10 12 15 18 22 27 33 39 47 56 68 82.
- Resistor SMD:
472=4.7 k ·4702=47 k ·4R7=4.7 Ω. - Cap code (pF):
104=100 nF ·103=10 nF ·102=1 nF ·220=22 pF. - Defaults: 0603/0402 for general SMD; 100 nF X7R decoupling per IC power pin; C0G for timing.