SMD Resistor Marking Systems
SMD resistors use compact numeric codes printed on the component body. The coding system depends on the tolerance and package size.
4-Digit — Used on 1% tolerance resistors. First three digits are the significand, fourth is the multiplier. 4702 = 470 × 10² = 47kΩ.
EIA-96 — Used on precision 1% resistors (small packages). Two-digit lookup code (01–96) plus a letter multiplier. 01C = 100 × 100 = 10kΩ.
R-Notation — For low values. The letter R marks the decimal point. 4R7 = 4.7Ω. R47 = 0.47Ω.
SMD Resistor Code Calculator
SMD (surface-mount) resistors are too small for colour bands, so they use printed numeric codes instead. The code system depends on the resistor’s tolerance: 5% parts use a 3-digit code, 1% parts use either a 4-digit code or the EIA-96 alphanumeric system, and very low values use R-notation where the letter R marks the decimal point. This calculator decodes any SMD marking to its resistance value, and encodes any resistance into all four code formats.
3-Digit Code (5% Tolerance)
The most common system. The first two digits are the significand (the value), and the third digit is the multiplier (the number of zeros to add).
103 → 10 × 10³ = 10 × 1000 = 10000 Ω = 10 kΩ
220 → 22 × 10&sup0; = 22 × 1 = 22 Ω
101 → 10 × 10¹ = 10 × 10 = 100 Ω
The third digit is NOT the third digit of the value — it is the power of ten. This is the most common mistake when reading SMD codes. 472 is not 472 Ω; it is 4700 Ω. For the through-hole equivalent using colour bands, see the Resistor Colour Code Calculator.
4-Digit Code (1% Tolerance)
The same system but with three significand digits for better precision. The first three digits are the value, the fourth is the multiplier.
1001 → 100 × 10¹ = 100 × 10 = 1000 Ω = 1 kΩ
2200 → 220 × 10&sup0; = 220 × 1 = 220 Ω
1000 → 100 × 10&sup0; = 100 Ω
4-digit codes appear on 1% tolerance resistors in larger packages (0805 and above). Smaller packages (0402, 0201) do not have enough space for four digits, so they use EIA-96 instead.
EIA-96 Code (1% Precision)
Two digits (01–96) look up a significand from a standardised table, and a letter sets the multiplier. This fits on the smallest packages where four digits would be unreadable.
68X → code 68 = 499, letter X = ×0.1 → 499 × 0.1 = 49.9 Ω
96B → code 96 = 976, letter B = ×10 → 976 × 10 = 9.76 kΩ
The 96 codes map to the E96 preferred value series (100, 102, 105, 107 … 953, 976). Each code covers one standard 1% value. The letter multipliers are: Z = ×0.001, Y/R = ×0.01, X/S = ×0.1, A = ×1, B = ×10, C = ×100, D = ×1000, E = ×10000, F = ×100000.
R-Notation (Low Values)
For resistances below 10 Ω, the letter R replaces the decimal point. This avoids confusion with the digit-multiplier system where low values would need a multiplier of 0.
R47 = 0.47 Ω
1R0 = 1.0 Ω
R10 = 0.10 Ω
R-notation is used for current sense resistors, power supply output shunts, and any application where milliohm or single-ohm precision matters. For current sensing applications with these low-value resistors, see the Current Sense Resistor Calculator.
Common SMD Codes Quick Reference
| Code | Value | Type |
|---|---|---|
| 000 | 0 Ω (jumper) | Zero-ohm link |
| R10 | 0.1 Ω | R-notation |
| 4R7 | 4.7 Ω | R-notation |
| 100 | 10 Ω | 3-digit |
| 101 | 100 Ω | 3-digit |
| 102 | 1 kΩ | 3-digit |
| 103 | 10 kΩ | 3-digit |
| 104 | 100 kΩ | 3-digit |
| 105 | 1 MΩ | 3-digit |
| 472 | 4.7 kΩ | 3-digit |
| 4702 | 47 kΩ | 4-digit |
| 01C | 10 kΩ | EIA-96 |
EIA-96 Multiplier Letters
| Letter | Multiplier | Example |
|---|---|---|
| Z | ×0.001 | 01Z = 0.1 Ω |
| Y or R | ×0.01 | 01Y = 1 Ω |
| X or S | ×0.1 | 01X = 10 Ω |
| A | ×1 | 01A = 100 Ω |
| B | ×10 | 01B = 1 kΩ |
| C | ×100 | 01C = 10 kΩ |
| D | ×1000 | 01D = 100 kΩ |
| E | ×10000 | 01E = 1 MΩ |
| F | ×100000 | 01F = 10 MΩ |
SMD Package Sizes
| Package | Size (mm) | Typical Marking |
|---|---|---|
| 0201 | 0.6 × 0.3 | None (too small) |
| 0402 | 1.0 × 0.5 | EIA-96 or none |
| 0603 | 1.6 × 0.8 | 3-digit or EIA-96 |
| 0805 | 2.0 × 1.25 | 3-digit or 4-digit |
| 1206 | 3.2 × 1.6 | 4-digit |
| 2512 | 6.3 × 3.2 | 4-digit |
Smaller packages have less space for markings. The 0201 (0.6 mm long) is unmarked — you rely entirely on the PCB placement and bill of materials. The 0402 may carry an EIA-96 code or be unmarked. From 0603 upward, most resistors carry a readable code. To check the resistance using the fundamental V = IR relationship, see the Ohm’s Law Calculator.
Reading Tips
Zero-ohm resistors are marked 000 or 0 or just a single line. They are wire jumpers used to cross traces on single-layer PCBs.
Context helps. If a code decodes to an unlikely value (e.g. 3.9 MΩ in a power supply), you are probably reading the wrong code system. Try the other format.
Use a magnifier. SMD markings on 0603 and smaller are barely visible to the naked eye. A 10× loupe or USB microscope makes identification much easier.
Frequently Asked Questions
Last updated: March 2026