SMD Resistor Code Calculator
This SMD Resistor Code Calculator converts common surface-mount resistor markings into resistance values. It supports 3-digit, 4-digit, EIA-96, R notation, and printed decimal formats.
The tool is useful for electronics engineers, PCB designers, technicians, repair teams, and students identifying components during assembly inspection, rework, reverse engineering, or circuit troubleshooting.
Each result includes the normalized code, notation type, human-readable resistance, formula, and step-by-step explanation so the marking can be checked rather than treated as a black-box lookup.
SMD Resistor Code Calculator
Enter a common SMD resistor marking and decode its resistance value, notation type, formula, and reading steps.
Example codes
Decoded resistance
10 kΩ
- Resistance value
- 10 kΩ
- Code type
- 3-digit code
- Normalized code
- 103
Explanation
10 provides the significant digits and 3 specifies the number of trailing zeros, or the power-of-ten multiplier.
10 × 10^3 = 10,000 Ω
- Read 10 as the significant value 10.
- Use the final digit 3 as the exponent: 10^3 = 1,000.
- Multiply 10 by 1,000 to obtain 10 kΩ.
Formula and Decoding Rules
3-digit code: R = AB × 10^M4-digit code: R = ABC × 10^MR notation: replace R with the decimal pointEIA-96: R = base value(NN) × multiplier(L)- AB = Two significant digits in a 3-digit code
- ABC = Three significant digits in a 4-digit code
- M = Final numeric digit used as a power-of-ten multiplier
- NN = EIA-96 index from 01 through 96
- L = EIA-96 multiplier letter
How to Decode an SMD Resistor Code
- Read the complete marking from the resistor body and enter it without spaces. Letter case does not matter.
- Select an example or press Decode. The parser identifies the notation from its length, digits, decimal marker, or EIA-96 multiplier letter.
- Review the code type before using the result. This is especially important when identifying precision EIA-96 components.
- Compare the decoded resistance with the schematic, BOM, and an isolated multimeter measurement where practical.
SMD Code Reference Table
Use this table to identify the expected code structure before decoding. The formula result is always expressed in ohms and then formatted with an engineering prefix.
| Code type | Structure | Decoding rule | Example |
|---|---|---|---|
| 3-digit code | ABM | AB is the two-digit value; M is the number of trailing zeros. | 472 = 47 × 10² = 4.7 kΩ |
| 4-digit code | ABCM | ABC is the three-digit value; M is the number of trailing zeros. | 1001 = 100 × 10¹ = 1 kΩ |
| R notation | A R B | R replaces the decimal point in a low resistance value. | 4R7 = 4.7 Ω; R22 = 0.22 Ω |
| Decimal notation | A.B | The printed decimal number directly represents resistance in ohms. | 0.22 = 0.22 Ω |
| EIA-96 code | NNL | NN selects an E96 base value; L selects the multiplier. | 01C = 100 × 100 = 10 kΩ |
Worked Example
For code 472, the first two digits form 47 and the final digit 2 means a multiplier of 10², or 100.
47 × 100 = 4,700 Ω = 4.7 kΩ.
For EIA-96 code 01C, index 01 selects base value 100 and C means ×100.
100 × 100 = 10,000 Ω = 10 kΩ.
These two systems can produce similar values, but their marking structures and intended resistor tolerance families are different.
Engineering Notes
- SMD markings normally identify resistance, not package size, power rating, voltage rating, pulse capability, or temperature coefficient.
- Many very small resistors have no printed marking. Use assembly documentation, placement data, or measurement instead of guessing.
- Codes 000 and 0000 commonly indicate a zero-ohm link rather than a conventional current-limiting resistor.
- EIA-96 is commonly associated with 1% resistor series, but the actual component specification must still be confirmed from manufacturing data.
- A two-digit code ending in R can be context-sensitive because R also exists as an EIA-96 multiplier letter. Confirm ambiguous markings against the BOM or package documentation.
Common Mistakes
- Reading the final numeric digit as a significant digit.
- Adding zeros to an EIA-96 index instead of using its lookup table.
- Ignoring R as a decimal marker in low-value resistor codes.
- Assuming the printed code includes tolerance or power rating.
- Measuring a resistor in-circuit without accounting for parallel paths.
FAQ
How do you read a 3-digit SMD resistor code?
Use the first two digits as the significant number and the third digit as the power-of-ten multiplier. For example, 103 means 10 × 10³ Ω, or 10 kΩ.
What does 4R7 mean on an SMD resistor?
The letter R replaces the decimal point, so 4R7 means 4.7 Ω. This notation keeps a small decimal mark clear on compact packages.
What is an EIA-96 resistor code?
EIA-96 is a three-character marking system used mainly for 1% resistors. Two digits select one of 96 standard base values and a letter supplies the multiplier.
Why do some SMD resistors use R instead of a number?
R is used as a visible decimal marker for low resistance values. Codes such as R22 and 4R7 are easier to print and inspect than tiny decimal points.
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Reference Links
Browse the resistor calculator category for component tools, or continue to the Engineering Reference Center for package and component-selection resources.
Disclaimer
This decoder provides nominal resistance values for engineering reference. Verify critical components with schematics, BOM data, manufacturer documentation, and an isolated measurement before use.