SMD Resistor Code Calculator

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Enter SMD Code

Supports 3-digit, 4-digit, and EIA-96 formats.

103

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About

Surface Mount Device (SMD) resistors use compact marking systems to denote resistance values due to their small surface area. Misinterpreting these codes leads to circuit failure, incorrect biasing, or thermal issues. This tool decodes the three primary standards used in modern electronics: the 3-Digit system (standard tolerance), the 4-Digit system (precision tolerance), and the EIA-96 system (1% precision).

Accuracy in reading these codes allows engineers to verify assembly specifications and hobbyists to salvage parts correctly. The logic distinguishes between numerical multipliers and specific alphanumeric codes like the EIA-96 standard, where a two-digit number references a lookup table rather than a direct value. This calculator handles standard multipliers, decimal placeholders, and specific tolerance indicators.

Formulas

The decoding logic depends on the format identified.

3-Digit Code (Standard 5% or 2%):

Formula: R = AB × 10^C

Where A and B are significant digits, and C is the multiplier. If R appears, it represents a decimal point.

4-Digit Code (Precision 1%):

Formula: R = ABC × 10^D

Where A, B, and C are significant digits, and D is the multiplier.

EIA-96 Code (Precision 1%):

Formula: R = Lookup(Code) × Multiplier

The code consists of two digits (01-96) mapping to a specific value from the E96 series, followed by a letter indicating the multiplier.

Reference Data

Code (EIA-96)	Significant Value	Multiplier Letter	Multiplier Factor
01	100	Z	0.001
02	102	Y or R	0.01
03	105	X or S	0.1
04	107	A	1
05	110	B or H	10
06	113	C	100
07	115	D	1000
08	118	E	10000
09	121	F	100000
10	124	-	-
11	127	-	-
12	130	-	-
13	133	-	-
14	137	-	-
15	140	-	-

Frequently Asked Questions

The letter "R" acts as a decimal point. For example, a code "4R7" translates to 4.7 Ohms. This is used because printing a tiny dot on a small component is unreliable and hard to see.

An underline usually indicates a specific manufacturer preference or that the resistor values read from the other direction (though rare). In some systems, a line under the code "R" or similar characters can denote a specific temperature coefficient or tolerance, but for calculation purposes, the alphanumeric characters are the primary data.

If a code like "99X" is entered, it is not a valid EIA-96 code because the lookup table only goes from 01 to 96. Ensure you are reading the component orientation correctly. Sometimes numbers like "06" and "90" can be confused if read upside down.

Generally, yes. The 3-digit system is typically associated with the E24 series (5% tolerance). However, checking the specific datasheet of the manufacturer is the only way to be 100% certain, as some 2% parts also use this marking scheme.