Hopefully, if you’re an electronics enthusiast, hobbyist, or professional working with circuits, you will already know how important resistors are for controlling the flow of electric current.
The resistance value of such components is measured in ohms, as indicated by coloured bands on the given resistor’s side.
These bands follow a standard system to convey critical information about the properties of the resistor. Those vital properties encompass not only the resistance value, but also the tolerance, and sometimes even the temperature coefficient.
In this article, then, we will set out how you can “read” these resistor colour bands with minimal time and effort. From there, you will be able to turn your attention to the creative aspects of your projects, instead of having to spend too much time on manual calculations.
The Resistor Colour Code Conversion Table, At A Glance
| 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 | +0.1% |
| Grey | 8 | 100M | +0.05% |
| White | 9 | 1G | – |
| Gold | – | 0.1 | +5% |
| Silver | – | 0.01 | +10% |
The Steps of Reading Resistor Colour Bands
Using a four-band resistor as an example, let’s set out the stages of how to read it:
- Identify the first band. This will be the first digit of the resistance value. So, if – for example – this first band is red, the first digit will be 2.
- Note the second band. This is the second digit. Let’s imagine, for instance, that it’s blue – in which case, the resistance value’s second digit will be 6.
- Look at the third band. This is the multiplier. If this band is orange, it will represent 103 (1,000). Multiplying the two-digit number (e.g. 26) by this number will give the resistance in ohms: 26 x 1,000 = 26,000 Ω (or 26 kΩ).
- Check the fourth band. This indicates the tolerance. If, for example, this is gold, the tolerance will be +5%. It means the actual resistance could be 5% above, or 5% below, the calculated value.
How Is the Process Different When Reading a Five-Band Resistor?
A similar process to the above applies to the reading of a five-band resistor. The difference is that the first three bands will represent digits, the fourth will be the multiplier, and the fifth will be the tolerance.
This means that if the band colours of a five-band resistor are brown, black, red, green, and brown, these will translate to the following:
- The resistance value being 102, given that brown, black, and red correspond in the above table with the digits 1, 0, and 2 respectively.
- The multiplier being 105, or 100,000, due to the fourth band being green.
- The resistance being 10,200,000 Ω, or 10.2 mega-ohms (Ω). This is because the relevant calculation would be 102 x 100,000.
- The tolerance being +1%, given that the fifth band is brown.
What About the Situation for A Six-Band Resistor?
As is the case with a five-band resistor, if it is a six-band resistor that needs to be read, the first three bands will be the significant digits, the fourth band will be the multiplier, and the fifth band will indicate the tolerance.
The sixth band signals the temperature coefficient. This refers to the degree to which the resistor’s actual resistance value changes when the temperature changes, as is relevant for specialised applications.
How Can a Resistor Colour Code Calculator Help?
Simply by Googling a term like “resistor colour code calculator”, you can quickly find an online tool that saves you from having to always remember the entire colour code chart.
A resistor colour code calculator, such as the one on the website of electrical component supplier RS, can speed up the process of decoding each band, by enabling you to input the colours into the tool.
After providing the respective numbers, you’ll just need to hit the “Calculate” button, to be instantly presented with the resistor value.
Final Thoughts You’ll Be Cracking That Code in Almost No Time
Getting to grips with the colour codes on resistor bands is much like learning a language, in that once you get the hang of it, you will be deciphering what such bands mean within seconds on each occasion.
Regardless, it is well worth bookmarking a resistor colour code calculator, just in case you need it for future projects. After all, even if you’re confident about what a particular set of resistor bands signify, there is no harm in double-checking with the help of a reputable tool.
