How to Read Resistor Colour Codes Right First Time

How to Read Resistor Colour Codes Right First Time

Is it just me or are resistors (especially 5-band variety) hard to orientate (left-to-right) so that reading the right code is straightforward? For years I’ve been throwing resistors into a pot on my bench when I remove them from a breadboard because, at the price, it’s easier to take a known value from a drawer than decipher an existing one – that is going to change!

A handful of resistors read something sensible either way up and so it is not as simple as “read both ways and pick the one that matches one of the standard values”.

I’ve listed all the facts and helpful tips in one place so I can refresh my memory easily:

  1. Know the colour codes, fact not tip – obviously. 0-9: Black, Brown, rainbow-no-indigo (ROYGBIV), Grey, White
  2. Remember that no codes start with gold or silver – if there’s a gold or silver band then that’s the end of the code
  3. Black, Orange, Yellow and White are not valid tolerance bands so resistors don’t end with these colours – if the last band is one of these then it’s probably upside down.
  4. Not usually of much help because there’s often no discernible gap, but if there’s a larger gap between first and second than between last and penultimate then its probably upside down. The tolerance band is sometimes separated from the values by a slightly larger gap
  5. 1% & 2%, 5-band, E96 resistors are low-cost and easy-to-find so they’re common. That means there are a lot of resistors with a red or brown tolerance band
  6. The tolerance band is sometimes wider – if there’s a wider band it should be to the right
  7. 6-band resistors are not common and the sixth band is the temperature coefficient so simply check the chart for the few occasions you find one. Note that the tips then apply to five of the bands for getting the orientation right.
  8. As the penultimate band is always either tolerance or multiplier (on almost all resistors) and Grey and White never represent either then the penultimate band is almost never grey or white – if the penultimate band is grey or white then its probably upside down.

Summary

Gap to the right, widest band to the right (but frequently not discernible)

Silver, Gold to the right

Red or brown often, but not conclusively, to the right

Black, Orange, Yellow, White to the left (unless there are 6 bands)

Grey, White in second place rather than last but one

Bl Br ROYGBV Gr Wh

Useful links

https://www.electronicsplanet.ch/en/electronics/resistor-color-code-reading-direction/resistor-color-code-reading-direction.php

https://www.arrow.com/en/research-and-events/articles/resistor-color-code

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