SMD Resistor Codes Explained — 3-Digit, 4-Digit, EIA-96

Surface-mount resistors are tiny. The largest common size (0805) is 2mm × 1.25mm. The markings printed on them are even tinier. Unlike through-hole resistors with their color bands, SMD resistors use numeric codes — and there are four different coding systems depending on the precision and size of the component.

The SMD resistor code decoder handles all four formats. Type the code, get the value.

3-digit code

The most common system. Two significant digits plus a multiplier (power of ten).

Value = (first two digits) × 10^(third digit)

Code	Calculation	Resistance
100	10 × 10⁰	10 Ω
101	10 × 10¹	100 Ω
102	10 × 10²	1 kΩ
103	10 × 10³	10 kΩ
104	10 × 10⁴	100 kΩ
220	22 × 10⁰	22 Ω
331	33 × 10¹	330 Ω
472	47 × 10²	4.7 kΩ
683	68 × 10³	68 kΩ

Watch out: "100" is 10 Ω, not 100 Ω. The third digit is always the multiplier, even when it's 0 (meaning ×1).

4-digit code

Higher precision resistors (1% tolerance, E96 series) use three significant digits plus a multiplier.

Value = (first three digits) × 10^(fourth digit)

Code	Calculation	Resistance
1000	100 × 10⁰	100 Ω
1001	100 × 10¹	1 kΩ
1002	100 × 10²	10 kΩ
4700	470 × 10⁰	470 Ω
4702	470 × 10²	47 kΩ
2201	220 × 10¹	2.2 kΩ

The trap: "1000" is 100 Ω (100 × 10⁰), while "1001" is 1 kΩ (100 × 10¹). The last digit is the multiplier, not part of the value.

R-notation (for values under 100 Ω)

When the resistance is below 100 Ω, the decimal point would be ambiguous in a pure numeric code. The letter "R" replaces the decimal point.

Code	Resistance
R47	0.47 Ω
1R0	1.0 Ω
4R7	4.7 Ω
10R	10 Ω
22R	22 Ω
47R	47 Ω

This system is unambiguous and easy to read — "4R7" is immediately recognizable as 4.7 Ω.

EIA-96 code

The EIA-96 system is used on high-precision 1% resistors. It combines a two-digit number (01–96) with a letter multiplier.

The two digits map to a specific value from the E96 series:

Code	Value	Code	Value	Code	Value
01	100	17	147	49	316
02	102	18	150	50	324
03	105	19	154	51	332
04	107	20	158	52	340
05	110	25	178	60	412
06	113	30	200	70	523
07	115	35	226	80	681
08	118	40	255	90	866
10	124	45	287	96	976

The letter indicates the multiplier:

Letter	Multiplier
Z	×0.001
Y or R	×0.01
X or S	×0.1
A	×1
B	×10
C	×100
D	×1,000
E	×10,000
F	×100,000

Example: "01C" = 100 × 100 = 10,000 Ω = 10 kΩ

Example: "10A" = 124 × 1 = 124 Ω

This system is compact but requires a lookup table — or the decoder tool.

How to tell which system is used

1. 3 characters, all digits → 3-digit code (e.g., 103, 472)
2. 4 characters, all digits → 4-digit code (e.g., 1002, 4702)
3. Contains "R" → R-notation (e.g., 4R7, R47, 10R)
4. 2 digits + 1 letter → EIA-96 (e.g., 01C, 96A)

Some 0201 and 01005 packages are too small for any marking at all. In that case, you need the BOM, pick-and-place file, or a precision LCR meter.

Reading SMD markings in practice

The numbers are often less than 1mm tall. Tips:

• Use magnification. A loupe, microscope, or phone camera macro mode.
• Good lighting. Angle a bright light to create contrast against the dark marking.
• Orientation. The marking can be read in any direction — there's no "right way up" like color-coded resistors. Context (the circuit or BOM) determines whether "102" is 1 kΩ or if you're reading it upside down as "201" (200 Ω).
• When in doubt, measure. A multimeter across the pads gives you the actual value. If the component is soldered in-circuit, measure with power off and be aware that parallel paths through the circuit can affect the reading.

Through-hole vs. SMD codes

Feature	Through-hole	SMD
Coding system	Color bands	Numeric/letter codes
Readable without tools	Yes (if you know the colors)	Often needs magnification
Orientation matters	Yes (read from tolerance band)	No
Values under 10 Ω	Gold/silver multiplier bands	R-notation
Precision variants	5-band	4-digit or EIA-96

Working with through-hole parts? The resistor color code decoder handles 4-band and 5-band resistors with a visual band selector.