Resistor Color Code Quick Guide

Closeup of a GE 531X Power Supply Board with banded resistors.
GE Motor Field Power Supply Board uses banded resistors.

If you’ve ever had to figure out a resistor color code–the value, tolerance, and wattage of multiple resistors, you know how mentally exhausting it can become. Mnemonic devices aside, sometimes it’s simpler to have a visual guide to help. 

This tool is designed to decode color-banded axial lead resistors with four or five bands.  You can use the number of bands and the colors along with the charts below to determine the value and tolerance of the resistors.

Feel free to make use of our favorite Resistor Color Code Guide, available below.  Right-click for a higher-definition view.


Resistor Color Code chart

How to Read Resistor Color Code

Four banded resistors have two bands for resistance, one multiplier band, and one band for tolerance. Five band resistors have an extra color band added to the first and second resistance digits. This gives you a more precise reading. Everything else shifts to the right, so the fourth band becomes the multiplier and the fifth becomes the tolerance.

Super simple, right?

Also, remember to take a good look at the body of your larger resistors to see what information is available to you. Many resistors are marked with their resistance value, tolerance, and wattage resistance if their body is large enough.

British Standard Code

Larger power resistors may use BS1852 British Standard Code, which uses suffix letters to replace part of the number to minimize misreading the position of the decimal point. This system uses “K for thousands or kiloohms and the letter M for millions or megaohms. R is used to denote a decimal point for resistor values of less than one. Thus:

  • 0.01Ω = R010 or 0R01
  • 1.0Ω=1R0
  • 24.9Ω=24R9
  • 4.7KΩ = 4K7
  • 470KΩ = 470K or 0M47
  • 1MΩ = 1M0

Tolerance Letters

Tolerance letters take the place of written out percentages. Tolerances also use K and M, so be sure when reading the code to know which letter refers to resistance value and which to tolerance.

  • B = 0.1%
  • C = 0.25%
  • D = 0.5%
  • F = 1%
  • G = 2%
  • J = 5%
  • K = 10%
  • M = 20%

Finally, remember the first band is typically the one closest to a lead, while the tolerance, which is always gold or silver, is the last band. This will help you understand which way to “read” the bands.

Carbon resistors are the most common type of resistor used within electronics. Carbon resistor color code is the standard resistor color code shown on this page.

And if there’s ever any doubt, you can measure resistance with a multi-meter.

Answers to a few commonly asked questions about resistors

What are the different types of electrical resistors?

  • Wire Wound Resistor–constantan or manganin wire wound around an insulating cylinder.
  • Metal Film Resistor–carbon or metal deposited as a thin film on to an insulating core.
  • Carbon Composition Resistor–mainly made of carbon clay covered with a plastic case. Very temperature sensitive.
  • Carbon Film Resistor
  • Variable Resistor–resistance value can be adjusted. A rheostat is one example.
  • Varistor–non-linear component where resistance changes with applied voltage.
  • Thermistor–resistance value changes with a change in temperature
  • Light Dependent Resistor–resistance varies depending on intensity of light.

Does a resistor consume energy?

Yes. As they do their primary job (control the flow of energy) they also consume some of the energy. A good example of this is the filament of a traditional light bulb, which lights up because it resists the flow of energy moving through it. But it also puts out heat (as anyone who has tried to change a burning light bulb can attest.)

Do resistors have polarity?

Current flows from positive to negative according to current direction. So resistors on their own do not have polarity in the sense they can connect to a circuit in either direction. But current can only flow in a single direction.

Legacy Systems: When You’ve Lost Documentation

Stacks of manuals for obsolete industrial equipment.  Manuals for legacy systems are important.
When you’ve had equipment for years, it’s easy to misplace the manual.

Imagine: you need to make a complex repair on a legacy system, but no one in your facility has any experience with the job.

Sometimes, all you need is that one piece of information to make everything work the way it should. But what happens when you’ve lost the manual that goes with your legacy system and the OEM no longer supports that model? You know your equipment will work exactly as it should if only you can track down that one setting.

What are Legacy Systems?

Legacy systems are made up of older technology no longer supported by the original equipment manufacturer. They make up the backbone of thousands of companies around the globe.   Replacement of these systems can be very expensive and challenging. And because of the inherent robust nature of industrial equipment, it often seems wasteful to remove a system in good working order.

Industrial-Strength | adjective

marked by more than usual power, durability, or intensity.

How Can I Get Documentation?

If we carry parts for your legacy system, we may be able to help with documentation replacement with your orders. While our in-house experts are knowledgeable about all things related to automation, they like having the manuals at their disposal, too.  We’re happy to help your in-house experts have the same advantage. Just ask when you call to place your next order.

So we….well, we’ve developed hoarder instincts when it comes to legacy documentation: if it’s going to be useful at some point down the road, we’ll grab a copy and keep it safe. 

That’s not a bad instinct if you think about it. With manuals at our side, we check every reconditioned unit leaving our facility. That way, when those Directlogic PLC ,   Reliance drive, or Reliance Automax PLC components reach you, they’re in excellent working condition.

So if you need documentation, let us know when you place your next order. For now, I’m going to end this post with a link to the User’s Manual (GFK-1065F) which is for one of our more popular items, a GE Fanuc Series 90 Micro PLC. It has full chapters devoted to the subjects of installation, configuration, and diagnostics, along with additional links to an ABB PVI-3.0/3.6/4.2 inverter

AX Control specializes in legacy equipment. We carry industrial automation replacement parts from GE, Fuji, and Reliance, to name just a few. Let us know what we can help you with today.