Resistor Codes

Resistors are color-coded and have at least two value bands and a multiplier; other bands are optional. To distinguish left from right there often is a gap after the multiplier band ¹.

Surface-mount resistors have a 3-digit or 4-digit code on them instead. The first two or three digits are the first digits of the answer. The last digit represents the multiplier. The answer is in Ohms. For example: 334 means 33×10⁴ Ω = 330 KΩ. Note that 100, 220 and 470 are 10 Ω, 22 Ω and 47 Ω respectively. Sometimes simply the 2-digit codes 10, 22 and 47 (without any multiplier) are printed on the resistor instead to avoid confusion. Another way to avoid mistakes is to print 10R, 22R or 47R on them. Often the letters K and M are used as well, e.g. 473 = 47K = 47 KΩ and 105 = 1M = 1 MΩ. The letters R, K and M are also used instead of a comma, e.g. 2K2 = 2,2 KΩ and 0R56 or simply R56 is an 0.56 Ω resistor.

However, making matters confusing, there’s a new coding system for SM resistors using a 2-digit code in combination with a multiplier letter. To decipher these, you’ll need the lookup tables below.

• with 1% type SM resistors the multiplier letters comes after the digits, e.g. 22A is a 165 Ω resistor, 68C is a 49900 Ω or 49.9 KΩ (49K9) one and 43E a 2740000 Ω or 2.74 MΩ (2M74) one
• 2% and 5% type resistors use alternative lookup tables and—to distinguish from 1% type resistors—the multiplier letter goes first, e.g. C31 is 5%, 18000 Ω (18K), and D18 is 510000 Ω (510K) 2% tolerance