About the SMD Resistor Code Calculator
This SMD resistor code calculator reads the tiny markings printed on surface-mount resistors and tells you the resistance. It understands all the common schemes: 3-digit codes such as 103 (10 kΩ), 4-digit precision codes such as 4702 (47 kΩ), codes that use R as the decimal point such as 4R7 (4.7 Ω) or R010 (10 mΩ), and the compact EIA-96 system used on 1% parts in 0603 and smaller packages, such as 01C (10 kΩ).
Switch to encode mode to go the other way: enter a resistance in ohms and see the 3-digit, 4-digit and EIA-96 markings it would carry, which is useful when searching a reel, checking a BOM or reworking a board. A marking of 0, 00 or 000 is a zero-ohm jumper.
Markings alone do not always reveal tolerance; the values shown are the typical tolerance associated with each scheme. Some manufacturers use their own codes, and very small 0201/01005 parts are often unmarked, so confirm critical values with a meter.
How to use the smd resistor code calculator
- 1Read the marking on the resistor with a magnifier (rotate the board if needed).
- 2Type it exactly as printed, e.g. 103, 4702, 4R7 or 01C.
- 3Read the resistance, the marking system and the typical tolerance.
- 4To find a code instead, switch to encode mode and enter the value in ohms.
Formula and method
Standard 3-digit codes give two significant digits followed by a power-of-ten multiplier, so 472 means 47 × 10² = 4,700 Ω. Precision parts use four digits — three significant digits and a multiplier — so 1002 is 100 × 10² = 10 kΩ. For values below 10 Ω (3-digit) or 100 Ω (4-digit) the letter R marks the decimal point: 4R7 = 4.7 Ω, R100 = 0.1 Ω.
EIA-96 fits a 1% value onto tiny parts with only three characters: the two digits (01–96) are an index into the E96 series of preferred values (01 = 100, 02 = 102 … 96 = 976), and the letter is a multiplier from Z (× 0.001) to F (× 100,000). So 01C is 100 × 100 = 10 kΩ and 68X is 499 × 0.1 = 49.9 Ω. Encoding reverses the process, reporting “—” where a value cannot be expressed in that scheme.
- AB, ABC
- Significant digits
- C, D
- Power-of-ten multiplier digit
- R
- Decimal point position
- NN
- EIA-96 index 01–96 into the E96 table
Worked examples
Decode 103
103 is a 3-digit code: 10 followed by three zeros, 10 × 10³ = 10,000 Ω = 10 kΩ. The same value is 1002 in the 4-digit scheme and 01C in EIA-96 (index 01 = 100, C = × 100).
Decode 4R7
The R stands for the decimal point, so 4R7 is 4.7 Ω. It is common on low-value current-sense and gate resistors.
Decode the EIA-96 code 68X
Index 68 in the E96 table is 499, and X multiplies by 0.1, giving 49.9 Ω. It needs three significant digits, so there is no 3-digit code for it; the 4-digit marking would be 49R9.
Find the codes for 4.7 kΩ
4,700 = 47 × 10², so the 3-digit code is 472, and 470 × 10¹ gives 4701. 470 is not an E96 value (the nearest are 464 and 475), so 4.7 kΩ has no EIA-96 code.
Frequently asked questions
What does 103 mean on an SMD resistor?+
103 means 10 followed by 3 zeros: 10,000 Ω or 10 kΩ. In 3-digit codes the first two digits are the significant figures and the third is the number of zeros to add.
What does the R mean in an SMD resistor code?+
R marks the position of the decimal point for values with a fractional part. 4R7 is 4.7 Ω, 1R0 is 1 Ω, R22 is 0.22 Ω and R010 is 0.010 Ω (10 mΩ).
How do I read EIA-96 resistor codes?+
EIA-96 codes are two digits plus a letter. Look up the two digits (01–96) in the E96 table to get a three-digit value, then multiply by the letter: Y = 0.01, X = 0.1, A = 1, B = 10, C = 100, D = 1,000, E = 10,000, F = 100,000.
What is a 000 or 0 SMD resistor?+
A resistor marked 0, 00 or 000 is a zero-ohm jumper. It is used as a link on circuit boards so pick-and-place machines can fit it like any other part, and often as a configuration option.
Do 4-digit codes mean 1% tolerance?+
Usually yes. 4-digit markings and EIA-96 codes are normally used on 1% (or tighter) resistors, while 3-digit codes are typical of 5% parts, but the datasheet or reel label is the only definite source.