SMD Resistor Code Calculator

RESISTOR CODE FORMAT

Standard 3-digit code: the first two digits are significant, the third digit is the multiplier (power of ten) in ohms. “R” is used as a decimal point for values below 10 Ω (for example 4R7 = 4.7 Ω).

4-digit code: the first three digits are significant, the fourth is the multiplier. “R” is used as a decimal point (for example 10R0 = 10.0 Ω).

EIA-96 code (±1%): two digits (01–96) select a base value from the E96 series, and the letter is a multiplier (for example 38C = 243×100 Ω = 24.3 kΩ).

Resistance

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Understanding SMD resistor markings

SMD resistors use compact numeric or alphanumeric markings to represent their resistance value. These markings vary by size, manufacturer and tolerance series, and correctly decoding them is essential for PCB assembly, troubleshooting and BOM verification.

This calculator interprets 3-digit, 4-digit, and R-notation resistor markings, converting them into resistance values in ohms (Ω), kilohms (kΩ) and megohms (MΩ).

How SMD resistor codes work

The most common markings are based on EIA-96 and basic 3- or 4-digit formats. The marking itself depends on tolerance and package size.

3-digit code (XYZ)

X and Y = significant digits
Z = multiplier (10^Z)

Formula:

R = (XY) × 10^Z Ω

Example:

Code: 472
(47) × 10² = 4700 Ω = 4.7 kΩ

4-digit code (WXYZ)

W, X, Y = significant digits
Z = multiplier

Formula:

R = (WXY) × 10^Z Ω

Example:

Code: 1001
100 × 10¹ = 1000 Ω = 1 kΩ

R-notation (decimal point)

The letter R indicates the decimal point and is commonly used for low-value resistors.

4R7 → 4.7 Ω
0R5 → 0.5 Ω
R10 → 0.10 Ω

No-mark or “blank” resistors

Extremely small packages (0201, 01005) often have no markings. Their value must be referenced from reel labels or documentation.

Common SMD resistor code examples

Marking	Resistance	SI Units
100	10 Ω	10 Ω
221	220 Ω	0.22 kΩ
472	4700 Ω	4.7 kΩ
105	1,000,000 Ω	1 MΩ
4R7	4.7 Ω	4.7 Ω

Using the SMD Resistor Code Calculator

Enter the resistor marking: Type any 3-digit, 4-digit or R-notation code.
View the decoded resistance: The tool displays values in Ω, kΩ and MΩ instantly.
Verify for assembly or replacement: Use the decoded value to confirm BOM accuracy, validate rework, or troubleshoot incorrect resistor placements.

Engineering notes

Power rating is not printed on SMD resistors: The package size (0402, 0603, etc.) determines power handling.
Tolerance affects marking formats: 1% resistors may use 4-digit codes; 5% resistors often use 3-digit codes.
Very low-value resistors (current-sense shunts) may use R-notation or dedicated markings.
Temperature coefficient (TCR) is never included in the printed marking; check the datasheet for TCR values.

This calculator removes the guesswork from interpreting SMD resistor markings, helping engineers and technicians accurately identify components during design, debugging and assembly.

FAQ about SMD Resistor Code Calculator

Why do some SMD resistors not have any printed code?

Packages 0201 and smaller are too small for legible markings.

These parts are identified by reel labels, part numbers or measurement equipment, not by visual inspection.

Does the code indicate power rating or tolerance?

No. The printed marking typically indicates resistance only.

Power rating is defined by package size, and tolerance (1%, 5%, etc.) is determined from the datasheet, not the printed code.

Is R-notation only used for low-value resistors?

Mostly yes. R represents the decimal point and is used when the value is too small to fit the 3-digit multiplier format.

For example, 0R5 = 0.5 Ω.

High-value resistors never use R-notation.