Unlike Through hole resisors which use colored bands to determine the value, surface mount resistor have numbers and sometimes letters. I will teach you how to take those letters and digits and determine the value.

Looking at the image you see 4 resistors, the first being 391 the seconed 270 and the two at the bottom are the same 30R9. That does not stand for a 391 ohm , 270 ohm, and so on. The formula for breaking the code down is as follows.

1st value-2nd value-multiplier

3 9 1 = 390 ohm resistor

2 7 0 = 27 ohm resistor

2 3 3 = 23000 ohm or 23K ohm resistor

There are some resistors which have 4 digits. The formula is the same with the addition to a digit.

1st value-2nd value-third value-multiplier

2 3 5 3 = 235K ohm resistor

You may ask"why some have three diigits and some have four?" three digits typically means that the resistor is 5% tolerance the four digit typically means the resistor is 1% tolerance. If a letter is used to represent tolerance use the chart below.

B=.1%

C=.25%

D=.5%

F=1%

G=2%

J=5%

K=10%

M=20%

Z=80%

Now you will notice that the last two resistor have an "R" in the equation. The way to look at these is very simple. The R represents a decimal. So 30R9 is a 30.9Ohm resistor.

R23= .23 ohm

5R6= 5.6 ohm

45R3= 45.3 ohm

Of course you can read the values with a meter, but whats the fun in that? I hope you all learned something from this little write up.