Blog Entry

How to read the Resistor value

November 12, 2008 by rwb, under Electronics.

Resistor is one of the electronic component that used in electronic design for controlling the flow of electric current. The more it resists the small the electric current will flow and vice verse. The resistance value is measured in ohm which is named after Georg Simon Ohm who first define the well known Ohm law, the fundamental relationship among Resistance, Current and Voltage. The symbol of resistance is the Greek letter omega (Ω).

In the electronic circuit diagram, resistor is represent in this following symbol:

Most resistor value is coded in 4 color band or 5 color band as the following table:

Example 1: the 4 color band resistor have this following color:

1st Ring: Red (2)
2nd Ring: Violet (7)
4th Ring: Brown (x10)
5th Ring: Gold (5%)

This resistor value is: Red (2) Violet (7) x Brown (10) = 27 x 10 = 270 Ohm with tolerance of 5%

Example 2: the 5 color band resistor have this following color:

1st Ring: Red (2)
2nd Ring: Violet (7)
3rd Ring: Black (0)
4th Ring: Brown (x10)
5th Ring: Black (1%)

This resistor value is: Red (2) Violet (7) Black (0) x Brown (10) = 270 x 10 = 2700 Ohm or 2.7KOhm (read Kilo Ohm) with tolerance 1%.

Yet another example let’s say you have the 5 color band resistor with this following color:

1st Ring: Yellow (4)
2nd Ring: Violet (7)
3rd Ring: Black (0)
4th Ring: Black (x1)
5th Ring: Black (1%)

The resistor value is: Yellow (4) Violet (7) Black(0) x Black (1) = 470 x 1 = 470 Ohm with tolerance of 1%.

As I mention above that most of resistor value use the color band code, but some of resistor such as surface mounted resistor used this following numeric code for it’s value: