Identify the resistance and tolerance of axial-lead resistors using standard color bands.
⚠️ 4-band and 5-band only. This tool does not support 6-band resistors (with temperature coefficient band), 3-band format, or non-standard color schemes. Always verify by physical inspection or with a multimeter.
Standard axial-lead resistors use color bands to indicate their resistance value and tolerance. The bands are read from left to right. The first few bands represent the significant digits, the second-to-last band is the multiplier (power of 10), and the final band is the tolerance.
4-Band Resistors: Two digit bands, one multiplier, and one tolerance band.
5-Band Resistors: Three digit bands, one multiplier, and one tolerance band. These are usually high-precision resistors.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | 100 | - |
| Brown | 1 | 101 | ±1% |
| Red | 2 | 102 | ±2% |
| Orange | 3 | 103 | - |
| Yellow | 4 | 104 | - |
| Green | 5 | 105 | ±0.5% |
| Blue | 6 | 106 | ±0.25% |
| Violet | 7 | 107 | ±0.1% |
| Grey | 8 | 108 | ±0.05% |
| White | 9 | 109 | - |
| Gold | - | 10-1 | ±5% |
| Silver | - | 10-2 | ±10% |
Look for a band that is slightly wider or physically separated from the others—that's usually the tolerance band (the end). Gold and silver bands are almost always tolerance bands and should be on the right. If unsure, identify the gold/silver band first, then read from the opposite end.
If a resistor only has 3 bands, the tolerance is assumed to be ±20% (brown). However, 3-band resistors are rare in modern use. Most practical resistors have 4 or 5 bands.
A zero-ohm resistor (marked with a single black band) is essentially a jumper wire encased in a component body. It's used on PCBs that are assembled by automated pick-and-place machines, allowing jumpers to be treated as regular components. It has negligible resistance (< 10 mΩ typically).
5-band resistors provide an extra significant digit, enabling precision to the tenths place. For example, a 5-band resistor can precisely represent 10.7 kΩ, while a 4-band can only represent 10 kΩ or 11 kΩ. This is essential for precision analog circuits, filters, and timing networks.
Tolerance bands indicate how much the actual resistance can deviate from the stated value due to manufacturing variations. Brown (±1%) and red (±2%) are tighter tolerances (higher quality/cost). Gold (±5%) and silver (±10%) are looser. For most applications, ±5% is adequate; precision circuits use ±1% or ±2%.
Generally, yes—a ±10% resistor can replace a ±5% one in most circuits, but it's less precise. However, using a tighter tolerance where a looser one is specified can waste money. Always follow the schematic specification. For critical circuits (oscillators, precision measurements), tight tolerance is essential.
Use a digital multimeter (ohmmeter function) to measure the actual resistance. This is always more reliable than reading faded color bands. Most color bands fade over time, especially with age or UV exposure. When in doubt, measure—it only takes seconds.
Temperature coefficient (typically in ppm/°C) describes how resistance changes with temperature. Standard resistors don't show this on color bands—it's found in datasheets. Precision resistors and some 6-band resistors include this information. It matters in high-temperature applications or when thermal stability is critical.
Related Tools
Calculate electrical values.
Calculate electrical voltage drop.
Calculate wire current capacity.
Calculate conduit wire capacity.
Calculate electrical box capacity.
Calculate box size.