Resistor color code calculator
Resistor color code calculatorThis calculator is a quick way to decipher the values of resistors marked with color bands. Simply select the number of bands and their colors, and the tool will immediately provide the resistance value. Indispensable in service, prototyping, and analysis of older circuits where descriptions may be unreadable or absent.
How does the color code on resistors work?
The color code is a universal system for marking resistance values, which eliminates the need for numeric printing on the component's casing. Mainly used in axial (THT) resistors, it is based on bands of different colors, each representing a digit, multiplier, or tolerance.
Depending on the number of bands, we distinguish:
- 3 bands – two digits and a multiplier,
- 4 bands – two digits, a multiplier, and tolerance,
- 5 bands – three digits, a multiplier, and tolerance,
- 6 bands – as above + temperature coefficient (ppm/K).
Reading always takes place in a specific direction – from the side where the bands are closer together and there is no silver or gold at the beginning.
Resistor color code table
| Color | Digit | Multiplier | Tolerance | Temp. coeff. (ppm/K) |
|---|---|---|---|---|
| Black | 0 | ×1 | — | 250 |
| Brown | 1 | ×10 | ±1% | 100 |
| Red | 2 | ×100 | ±2% | 50 |
| Orange | 3 | ×1,000 | — | 15 |
| Yellow | 4 | ×10,000 | — | 25 |
| Green | 5 | ×100,000 | ±0.5% | — |
| Blue | 6 | ×1,000,000 | ±0.25% | 10 |
| Purple | 7 | ×10,000,000 | ±0.1% | 5 |
| Gray | 8 | ×100,000,000 | ±0.05% | — |
| White | 9 | ×1,000,000,000 | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
| No band | — | — | ±20% | — |
Typical applications of color markings
The color code is primarily present in classic axial resistors (with wire leads). Despite the development of SMD technology, striped resistors are still widely used:
- in budget devices,
- in educational and DIY projects,
- in servicing older type equipment,
- when there is no room for printing or a label.
Their advantage is durability and readability, provided the colors do not fade or get covered by varnish, dust, or damage.
Reading the value of bands on resistors – what to watch out for?
Working with the color code may seem simple, but it's easy to make a mistake. Here are some common pitfalls:
- Wrong reading direction, e.g., considering the gold band as the first instead of the last;
- Similarity of colors - especially brown, red, and orange can be difficult to distinguish in poor lighting;
- Damage and dirt – bands may be unreadable after years of use. In old devices, bands may change shade due to heat, UV radiation, or aging of the varnish. Therefore, in service, it is often necessary to compare several similar components or measure the value directly;
- Lack of tolerance – older components may lack the fourth band.
In case of doubt, it is worth comparing with a catalog or simply measuring the resistance with a multimeter.
FAQ - frequently asked questions about resistor color codes
How to read the value from 4 bands?
The first two bands are digits, the third is a multiplier, and the fourth is tolerance. For example, red (2), purple (7), brown (×10), gold (±5%) = 270Ω ±5%.
What do the gold and silver bands mean?
Gold as a multiplier = ×0.1, and gold as tolerance = ±5%. Meanwhile, silver as a multiplier = ×0.01, and silver as tolerance = ±10%.
Are the bands always read from left to right?
Yes, but it's not about the physical side of the component, but the arrangement of the bands. Usually, a larger gap on one side indicates the end of the color code. If the distance from the resistor ends is the same, look for the tolerance band – the color gold or silver will always be at the end.
What does the absence of the fourth band mean?
The absence of the tolerance band means a default of ±20% – used in the cheapest or older resistors.
Are the colors of the resistor bands universal?
Yes. The color coding used on resistors is an international standard and applies regardless of the manufacturer or country of origin.
Did you know...
- Striped markings on resistors were developed in the 1920s by the American Radio Manufacturers Association (RMA). They were introduced because electronic components were becoming smaller. Inscriptions did not fit, so a colorful code was started – universal, readable, and recognizable without a magnifying glass. Today, 4-, 5-, and even 6-band codes are used. Additional bands inform about tolerance and temperature coefficient. It is one of the most successful electronics standards, which still works unchanged today.
- Some very precise resistors (e.g., 6-band) contain additional information about temperature stability – important in measuring devices.
- There are also striped markings for inductors and ceramic capacitors, but they have different rules. IEC 60062:2016 – "Marking codes for resistors and capacitors" is the official document establishing the coding of values for passive components, including the color code for resistors.
- In case of unclear markings, the reading direction can be assessed by the spacing of the bands – the first ones are always closer to one edge. Identifying the gold or silver band – usually at the end (as tolerance) – often helps.
- Colors in the stripe code do not directly indicate resistance values, only digits or multipliers, and the final value of the resistor results from their arrangement. For example, in the color code, orange represents the digit 3, not the value 3Ω – interpretation depends on the position of the band!
- The position of the color bands on a resistor can be easily remembered using mnemonics. There are dozens of funny or educational sentences in various languages that help remember the order of colors, such as in English, one of the more popular is "Big Boys Race Our Young Girls But Violet Generally Wins."
