SMD resistor

SMD resistors

Surface mounted resistors are printed with numerical values in a code related to that used on axial resistors. Standard-tolerance surface-mount technology (SMT) resistors are marked with a three-digit code, in which the first two digits are the first two significant digits of the value and the third digit is the power of ten (the number of zeroes). For example:

334	= 33 × 104 ohms = 330 kilohms
222	= 22 × 102 ohms = 2.2 kilohms
473	= 47 × 103 ohms = 47 kilohms
105	= 10 × 105 ohms = 1.0 megohm

Resistances less than 100 ohms are written: 100, 220, 470. The final zero represents ten to the power zero, which is 1. For example:

100	= 10 × 100 ohm = 10 ohms
220	= 22 × 100 ohm = 22 ohms

Sometimes these values are marked as 10 or 22 to prevent a mistake.

Resistances less than 10 ohms have 'R' to indicate the position of the decimal point (radix point). For example:

4R7	= 4.7 ohms
R300	= 0.30 ohms
0R22	= 0.22 ohms
0R01	= 0.01 ohms

Precision resistors are marked with a four-digit code, in which the first three digits are the significant figures and the fourth is the power of ten. For example:

1001	= 100 × 101 ohms = 1.00 kilohm
4992	= 499 × 102 ohms = 49.9 kilohm
1000	= 100 × 100 ohm = 100 ohms

000 and 0000 sometimes appear as values on surface-mount zero-ohm links, since these have (approximately) zero resistance.

More recent surface-mount resistors are too small, physically, to permit practical markings to be applied.