The_Official_Raspberry_Pi_-_Beginner’s_Book_Vol1,_2018 (1)

Chapter 6 Physical computing with Scratch and Python 125

THE OFFICIAL RASPBERRY PI BEGINNER’S GUIDE

Reading resistor colour codes
Resistors come in a wide range of values, from zero-resistance versions which are effectively
just pieces of wire to high-resistance versions the size of your leg. Very few of these resistors
have their values printed on them in numbers, though: instead, they use a special code printed
as coloured stripes or bands around the body of the resistor.

1st Band

2nd Band Multiplier

Tolerance

Black

Brown

Red

Orange

Yellow

Green

Blue

Violet

Grey

White

Gold

Silver

None

0 1 2 3 4 5 6 7 8 9 - - -

1st/2nd Band

×10¹

×10²

×10³

×10

×10

×10

×10

×10

×10

×10 -¹

×10 -²

Multiplier

• ±1%
  ±2%


• 
  


• 
  

  ±0.5%
  ±0.25%
  ±0.1%
  ±0.05%

  
  


• 
  

  ±5%
  ±10%
  ±20%

  
  

Tolerance

×10

To read the value of a resistor, position it so the group of bands is to the left and the lone
band is to the right. Starting from the first band, look its colour up in the ‘1st/2nd Band’ column
of the table to get the first and second digits. This example has two orange bands, which both
mean a value of ‘3’ for a total of ‘33’. If your resistor has four grouped bands instead of three,
note down the value of the third band too (for five/six-band resistors, see rpf.io/5-6band).
Moving onto the last grouped band – the third or fourth – look its colour up in the ‘Multiplier’
column. This tells you what number you need to multiply your current number by to get the