SMD Resistor Code Calculator — 3-Digit, 4-Digit & EIA-96 Decoder
This SMD resistor code calculator instantly decodes the resistance value from the alphanumeric code printed on surface-mount resistors. Below is a full explanation of all three coding systems.
What Is the SMD Resistor Code?
SMD (Surface Mounted Device) resistors are too small for the traditional color band system used on through-hole resistors. Instead, manufacturers print compact numeric or alphanumeric codes on the component surface. Three standards are in common use:
- 3-digit code — used on standard tolerance (±5%) resistors
- 4-digit code — used on precision (±1%) resistors
- EIA-96 code — 3-character alphanumeric system for ±1% resistors in small packages (0603 and below)
Formula: 3-Digit and 4-Digit Codes
In both systems, the first digits are significant figures and the last digit is the power-of-10 multiplier.
3-digit code ():
4-digit code ():
Special case — the letter R: When "R" appears in the code, it acts as a decimal point and no multiplier is applied. Examples:
4R7= 4.7 Ω,R22= 0.22 Ω,2R2= 2.2 Ω.
EIA-96 Code System
The EIA-96 system uses two digits + one letter (e.g., 01A):
- The two digits are an index into a table of 96 E96-series values
- The letter is the multiplier
| Letter | Multiplier | Letter | Multiplier |
|---|---|---|---|
| Y or S | 0.01 (×0.01) | B or H | 10 (×10) |
| X or R | 0.1 (×0.1) | C | 100 (×100) |
| A | 1 (×1) | D | 1000 (×1000) |
Common EIA-96 index values (partial):
| Code | Base value | Code | Base value |
|---|---|---|---|
| 01 | 100 Ω | 25 | 178 Ω |
| 02 | 102 Ω | 50 | 316 Ω |
| 10 | 124 Ω | 75 | 562 Ω |
| 96 | 976 Ω | — | — |
Step-by-Step Decoding Examples
Example 1 — 3-digit "103":
- Significant digits: D1=1, D2=0 → base = 10
- Multiplier: D3=3 → ×10³
- Value = 10 × 1000 = 10 kΩ
Example 2 — 4-digit "8202":
- Significant digits: D1=8, D2=2, D3=0 → base = 820
- Multiplier: D4=2 → ×10²
- Value = 820 × 100 = 82 kΩ
Example 3 — EIA-96 "01A":
- Code 01 → base value = 100
- Letter A → multiplier = ×1
- Value = 100 × 1 = 100 Ω
Example 4 — "4R7" (decimal R notation):
- R is a decimal point → 4.7 Ω = 4.7 Ω
Common SMD Resistor Packages
| Package | Size (mm) | Min. readable code |
|---|---|---|
| 2512 | 6.35 × 3.2 | 4-digit or EIA-96 |
| 1206 | 3.2 × 1.6 | 4-digit or EIA-96 |
| 0805 | 2.0 × 1.25 | 3 or 4-digit |
| 0603 | 1.6 × 0.8 | EIA-96 (printed) |
| 0402 | 1.0 × 0.5 | Usually unmarked |
| 0201 | 0.6 × 0.3 | Always unmarked |
Frequently Asked Questions
How do I tell if my SMD resistor uses EIA-96 or 3-digit coding?
EIA-96 codes always end in a letter with exactly two digits before it (e.g., 01A, 75C). Three-digit codes contain only numbers — unless the code contains an R as a decimal marker (e.g., 4R7), which is not EIA-96.
My SMD resistor has no markings. How do I identify it?
Packages 0402 and smaller are typically unmarked — the surface is too small for laser printing. Your only option is to measure with a multimeter (ohmmeter) or consult the manufacturer's reel labeling / PCB BOM.
What does a code like "000" mean?
000 (or 0000) on an SMD resistor means 0 Ω — it's a jumper or short circuit, used to bridge traces on a PCB without soldering a wire.
Are EIA-96 values the same as E96 series standard values?
Yes. The EIA-96 index table lists all 96 values in the E96 preferred number series, spaced approximately 2.5% apart from 100 to 976 (before applying the multiplier letter).