SMD resistor code calculator

Reading SMD resistor codes

Surface-mount resistors are too small for color bands, so they carry printed codes. There are three common systems:

• 3 digits (common ±5% parts): the first two digits are the value, the third is the number of zeros. 472 = 47 followed by 2 zeros = 4,700 Ω = 4.7 kΩ.
• 4 digits (±1% parts): three digits of value and one multiplier. 1002 = 100 followed by 2 zeros = 10 kΩ.
• EIA-96 (±1% parts in small packages): two digits pick a value from the E96 series and a letter is the multiplier. 01C = 100 × 100 = 10 kΩ.

Values below 10 Ω use R as the decimal point: 4R7 = 4.7 Ω, R100 = 0.1 Ω, as found on current-sense resistors.

Worked example

68X: index 68 in the E96 table is 499 and X means × 0.1, so the value is 49.9 Ω, a ±1% part.

The page recognises the coding system from the shape of the code. Three digits are two significant figures and a power-of-ten multiplier; four digits are three significant figures and a multiplier; R or M marks a decimal point in ohms or milliohms; and two digits followed by a letter are looked up in the EIA-96 table, whose 96 entries are the E96 series from 100 to 976, with the letter giving the multiplier. The result is shown with an SI prefix and in plain ohms, with the tolerance usually associated with that system, as defined in IEC 60062.