Takeaway
- 3-digit code (e.g. 472): first two digits = significant figures, third digit = power-of-10 multiplier. 472 = 47 × 10² = 4,700 Ω.
- 4-digit code (e.g. 4702): first three digits = significant figures, fourth digit = multiplier. 4702 = 470 × 10² = 47,000 Ω.
- EIA-96 (e.g. 01C): two-digit code (01–96) maps to a base value via lookup table; letter = multiplier. 01C = 100 × 100 = 10,000 Ω.
- R-notation (e.g. 4R7, R47): letter R marks the decimal point. 4R7 = 4.7 Ω; R47 = 0.47 Ω. Used for values below 10 Ω.
- Zero-ohm jumper: marked 0, 00, 000, or 0000 depending on package size. Not a short circuit — it has a defined current rating.
- 01005 and many 0201 resistors carry no markings at all — rely on reel label, BOM, or LCR meter for identification.
- Common misread: “100” = 10 × 10⁰ = 10 Ω (NOT 100 Ω). “101” = 100 Ω. “102” = 1,000 Ω (1 kΩ).
SMD resistors abandoned the four-band color code because below a few millimeters, color bands become physically impossible to apply and optically impossible to read. The replacement systems — 3-digit numeric, 4-digit numeric, EIA-96 alphanumeric, and R-notation — are compact, machine-readable, and unambiguous once you know the rules. This guide walks through each system with worked examples, provides the complete EIA-96 lookup table, covers zero-ohm jumpers and unmarked packages, and flags the most common misread pitfalls.
Why SMD Resistors Use Numeric Codes Instead of Color Bands
Through-hole resistors use a four-band (or five-band) color code because the bands can be printed large enough to read with the naked eye, and axial packages provide enough body length for four distinct colored rings. An 0805 SMD resistor (2.0 × 1.25 mm) could theoretically carry color bands, but an 0402 (1.0 × 0.5 mm) cannot — and a 0201 or 01005 package is smaller than the dot at the end of this sentence.
Numeric codes solve this by printing compact characters (typically 1–2 mm tall) that are readable by automated optical inspection (AOI) systems and vision-guided pick-and-place machines, not just human technicians. They also eliminate the ambiguity of color perception under different lighting conditions. Three marking standards have been established by the EIA (Electronic Industries Alliance) and adopted globally: the 3-digit system for general-purpose 5% tolerance resistors, the 4-digit system for 1% precision resistors, and the EIA-96 system for precision resistors in packages too small for 4-digit codes.
3-Digit Code: Reading E24 Series Resistors
The 3-digit marking system is the most common and covers the vast majority of general-purpose SMD resistors at 5% tolerance (E24 value series). The rule is straightforward:
3-Digit Rule: [D1][D2][M] – D1 and D2 = the two significant figures. – M = the power-of-10 multiplier (number of zeros to append). – Resistance = (D1D2) × 10^M Ω
3-Digit Code Examples
| Marking | Significant Figures | Multiplier (10^M) | Resistance |
| 100 | 10 | 10⁰ = 1 | 10 Ω |
| 101 | 10 | 10¹ = 10 | 100 Ω |
| 102 | 10 | 10² = 100 | 1,000 Ω (1 kΩ) |
| 472 | 47 | 10² = 100 | 4,700 Ω (4.7 kΩ) |
| 103 | 10 | 10³ = 1,000 | 10,000 Ω (10 kΩ) |
| 474 | 47 | 10⁴ = 10,000 | 470,000 Ω (470 kΩ) |
| 105 | 10 | 10⁵ = 100,000 | 1,000,000 Ω (1 MΩ) |
| 000 / 0 | 0 | — | 0 Ω (zero-ohm jumper) |
4-Digit Code: Reading E96 Series 1% Resistors
The 4-digit system extends the 3-digit approach by adding a third significant figure, enabling the finer resistance steps needed for 1% tolerance precision resistors. It appears on packages 0805 and larger where there’s enough body space for four printed characters.
4-Digit Rule: [D1][D2][D3][M] – D1, D2, D3 = the three significant figures. – M = the power-of-10 multiplier. – Resistance = (D1D2D3) × 10^M Ω
4-Digit Code Examples
| Marking | Significant Figures | Multiplier (10^M) | Resistance |
| 1000 | 100 | 10⁰ = 1 | 100 Ω |
| 1001 | 100 | 10¹ = 10 | 1,000 Ω (1 kΩ) |
| 4702 | 470 | 10² = 100 | 47,000 Ω (47 kΩ) |
| 2203 | 220 | 10³ = 1,000 | 220,000 Ω (220 kΩ) |
| 1004 | 100 | 10⁴ = 10,000 | 1,000,000 Ω (1 MΩ) |
| 0000 | 0 | — | 0 Ω (zero-ohm jumper) |
Note that the 4-digit system and the EIA-96 system both target 1% tolerance resistors (E96 series) but use fundamentally different encoding approaches. The 4-digit system encodes the value directly; EIA-96 uses a lookup table. Which system appears on a given part depends on the manufacturer’s preference and the available marking area on the package.
EIA-96 Alphanumeric Code: Reading Precision Resistors in Small Packages
The EIA-96 system was developed to encode 1% precision resistance values on packages too small to fit a 4-digit numeric code — primarily 0603 and smaller. Instead of encoding the value directly, EIA-96 uses a two-digit lookup code (01 through 96) that maps to one of 96 base resistance values in the E96 preferred value series, followed by a single letter that acts as a multiplier.
EIA-96 Rule: [NN][L] – NN = two-digit code (01–96) → look up the base value in the EIA-96 table below. – L = multiplier letter (see table). – Resistance = Base Value × Multiplier Ω
EIA-96 Multiplier Letter Reference
| Letter | Multiplier | Example (code 68 = 499) |
| Z | × 0.001 | 68Z = 499 × 0.001 = 0.499 Ω |
| Y or R | × 0.01 | 68Y = 499 × 0.01 = 4.99 Ω |
| X or S | × 0.1 | 68X = 499 × 0.1 = 49.9 Ω |
| A | × 1 | 68A = 499 × 1 = 499 Ω |
| B or H | × 10 | 68B = 499 × 10 = 4,990 Ω (4.99 kΩ) |
| C | × 100 | 68C = 499 × 100 = 49,900 Ω (49.9 kΩ) |
| D | × 1,000 | 68D = 499 × 1,000 = 499,000 Ω (499 kΩ) |
| E | × 10,000 | 68E = 499 × 10,000 = 4,990,000 Ω (4.99 MΩ) |
| F | × 100,000 | 68F = 499 × 100,000 = 49,900,000 Ω (49.9 MΩ) |
R-Notation: Reading Sub-10 Ω and Fractional Resistor Values
When resistance values are below 10 Ω (or occasionally below 100 Ω), the multiplier digit in the 3-digit or 4-digit code would be “0” or would require a decimal point — which is impractical to print on a small ceramic body. R-notation solves this by using the letter R as a decimal point marker within the value itself, replacing the multiplier-digit structure entirely.
R-Notation Examples
| Marking | Decoded Value | Notes |
| R10 | 0.10 Ω | 100 mΩ — typical current-sense shunt range |
| R47 | 0.47 Ω | Common in low-current sensing circuits |
| 1R0 | 1.0 Ω | Termination and damping resistors |
| 4R7 | 4.7 Ω | Pull-down / filter resistors |
| R001 | 0.001 Ω (1 mΩ) | High-current sensing; requires 4-wire (Kelvin) measurement |
| R005 | 0.005 Ω (5 mΩ) | Battery current monitoring in BMS applications |
| 47R0 | 47 Ω | Can also appear as plain 470 in 3-digit; manufacturer-dependent |
Current-sense resistors using milliohm R-notation values are a special case: at R001 (1 mΩ) and similar ultra-low values, lead resistance from PCB traces becomes comparable to the component resistance itself. Four-terminal (Kelvin) connection with dedicated force and sense pads eliminates trace resistance from the measurement path and is considered mandatory design practice for values below approximately R010 (10 mΩ).
Zero-Ohm Jumpers: Markings, Ratings, and Use Cases
A zero-ohm resistor is a standard SMD resistor package with a resistive element that has been intentionally manufactured to near-zero resistance. It serves as a programmable jumper on a single-sided or double-sided PCB, allowing trace routing to cross without adding a PCB layer or cutting slots through the board.
| Package | Typical Marking | Typical Current Rating |
| 0201 | 0 | Up to 500 mA |
| 0402 | 0 | Up to 1 A |
| 0603 | 000 | Up to 1 A |
| 0805 | 000 or 0000 | Up to 2 A |
| 1206 | 0000 | Up to 2 A |
| 2010 / 2512 | 0000 | Up to 3–5 A |
Zero-ohm jumpers have a measurable resistance (typically 20–50 mΩ) and a defined maximum continuous current rating. Using them above their rated current causes resistive heating and eventual failure — a common prototype debugging trap when engineers assume a zero-ohm device is truly a short circuit with unlimited current capacity. For high-current paths, use the largest available package or consider a copper pour bridge.
Unmarked Packages: What to Do with Blank 0201 and 01005 Resistors
The smallest SMD resistor packages — 01005 (0.4 × 0.2 mm) and many 0201 (0.6 × 0.3 mm) parts — are too physically small to carry any printed marking at all. The ceramic body provides less than 0.2 mm² of printable surface area. This is not a manufacturing defect; unmarked parts are the expected and normal specification for these package sizes.
Identification options when the body is blank: – Reel label: The tape-and-reel label carries the full part number, value, tolerance, and manufacturer information. Always retain and document reel labels before cutting tape. – Bill of Materials (BOM): The BOM and centroid/pick-and-place file specify exactly which value goes on each reference designator. This is the authoritative source during assembly. – LCR meter measurement: An LCR meter with Kelvin clips can measure resistance to verify an unmarked part’s value, though accuracy at values below 1 Ω requires a four-terminal fixture. – AOI and X-ray: Automated optical inspection systems can’t read markings that don’t exist; they instead verify component placement position and pad coverage. Component identity verification for unmarked parts relies entirely on reel traceability. – Incoming inspection protocol: For unmarked 0201/01005 components, implement a tape-cut-verification procedure: measure resistance from the same reel position before cutting tape into a mixed-component area.
Technical Specifications
| Parameter | Value / Range |
| Package sizes | 01005 (0.4×0.2 mm), 0201, 0402, 0603, 0805, 1206, 1210, 2010, 2512 |
| Power rating | ~0.02 W (01005) to 1 W (2512); typical: 0.063 W (0402) – 0.25 W (1206) |
| Standard tolerance grades | ±5% (E24 / 3-digit), ±1% (E96 / 4-digit or EIA-96), ±0.1%–0.5% (precision) |
| Resistance range | 0 Ω (zero-ohm jumper) to ~10 MΩ |
| Temperature coefficient (TCR) | ±100–200 ppm/°C (thick-film general); ±10–50 ppm/°C (thin-film precision) |
| Operating temperature range | −55°C to +155°C (standard); −55°C to +175°C (AEC-Q200 automotive) |
| Marking systems | 3-digit (E24/5%), 4-digit (E96/1%), EIA-96 alphanumeric (1% small packages), R-notation (sub-10 Ω) |
| Resistive film technology | Thick-film (RuO2 on Al2O3, cost-effective); thin-film (NiCr or TaN, precision) |
| Termination finish | Tin-plated (standard, RoHS); gold-plated (high-reliability); nickel-barrier (automotive) |
| Packaging format | Tape-and-reel (SMT production), cut tape (prototyping), bulk (through-hole compatible adapters) |
| Value series | E24 (5%), E48 (2%), E96 (1%), E192 (0.5% and tighter) |
| Compliance | RoHS 3 (EU 2011/65/EU); REACH (EC No. 1907/2006); AEC-Q200 (automotive qualification) |
Application Scenarios by Circuit Function
Pull-Up and Pull-Down Resistors
Pull-up and pull-down resistors define the logic default state of digital signal lines — I²C/SPI bus lines, reset inputs, open-drain outputs — when the driving device is in high-impedance (tri-state). Typical values: 4.7 kΩ to 10 kΩ (marked 472, 4701, or 01C). 0402 is the standard package for most digital designs; 0201 where board density demands it.
Voltage Dividers and Reference Bias
Precision voltage dividers for ADC reference inputs, comparator thresholds, and amplifier gain networks require matched pairs of 1% or 0.1% thin-film resistors. EIA-96 marked parts at 0603 or 0402 are standard. Ratio accuracy — not absolute value — typically governs tolerance selection; thin-film parts with matched TCR minimize drift over temperature.
Current-Sense Resistors
Low-value shunt resistors (R001 to R100, i.e. 1 mΩ to 100 mΩ) in 2010 or 2512 packages allow system current monitoring by measuring the voltage drop across the shunt. Four-terminal Kelvin connections are mandatory for values below R010 (10 mΩ). Power rating must be verified: a 50 mΩ shunt carrying 3 A dissipates 450 mW — confirming the 2512 package is required, not just recommended.
Impedance Matching and Termination
Series termination resistors (typically 22–33 Ω, marked 220 or 330) are placed in series with high-speed data lines (DDR, PCIe, USB) to match the trace impedance and reduce reflections. Shunt termination at the load uses 50 Ω or 100 Ω values to define the transmission line endpoint. Both require ±1% or better tolerance; thin-film preferred at frequencies above 1 GHz.
Automotive and Safety-Critical Applications
AEC-Q200-qualified thick-film or thin-film resistors with extended temperature ranges (−55°C to +175°C), low TCR, and defined qualification lot traceability are specified for ECU, ADAS, and BMS designs. PPAP documentation is required for Tier 1 automotive programs. Nickel-barrier terminations provide superior resistance to sulfuric acid environments in underhood locations.
Medical Device Measurement Circuits
Patient monitoring, infusion pump dosing circuits, and diagnostic AFE (analog front end) designs use 0.1% thin-film resistors in feedback and gain-setting networks where measurement accuracy directly affects clinical outcomes. TCR below 25 ppm/°C and long-term stability below 0.1% over the product lifetime are typical specifications.
SMD Resistor Marking System Comparison
| Attribute | 3-Digit Code | 4-Digit Code | EIA-96 Code | R-Notation |
| Typical tolerance | ±5% (E24) | ±1% (E96) | ±1% or tighter | Any (value-dependent) |
| Significant digits | 2 | 3 | 3 (via lookup table) | N/A (decimal position) |
| Typical package size | 0805, 1206 and larger | 0805 and larger | 0603 and smaller | All sizes (low-Ω parts) |
| Decoding method | Direct calculation | Direct calculation | Lookup table + letter | Direct (R = decimal point) |
| Best for | General-purpose circuits | Precision analog, feedback | Space-constrained precision | Sub-10 Ω, current sensing |
| Example | 472 = 4.7 kΩ | 4702 = 47 kΩ | 01C = 10 kΩ | 4R7 = 4.7 Ω |
Frequently Asked Questions
What does the SMD resistor code 472 mean?
In the 3-digit system, the first two digits (47) are the significant figures and the third digit (2) is the power-of-10 multiplier. 472 = 47 × 10² = 47 × 100 = 4,700 Ω (4.7 kΩ). This is one of the most common values in pull-down and voltage-divider applications. Don’t confuse it with 4702 (4-digit, same value 47,000 Ω = 47 kΩ) or with a plain 47 Ω resistor.
What is the difference between a 3-digit and 4-digit SMD resistor code?
The 3-digit code encodes two significant figures plus a multiplier and is used on 5% tolerance resistors in the E24 value series. The 4-digit code encodes three significant figures plus a multiplier, providing finer resolution for 1% tolerance resistors in the E96 value series. Both decode directly without a lookup table: the last digit is always the power-of-10 multiplier. The 4-digit code appears on 0805 and larger packages where there’s enough body space for four characters; 0603 and smaller 1% parts typically use EIA-96 instead.
How do I read an EIA-96 resistor code?
EIA-96 codes combine a two-digit numeric code (01 through 96) with a letter multiplier. The two-digit code maps to a base resistance value via the standardized EIA-96 lookup table (complete table included in this guide). The letter defines the multiplier: A = ×1, B or H = ×10, C = ×100, D = ×1,000, and so on. Example: code 68B → code 68 = base value 499 Ω × B (×10) = 4,990 Ω (4.99 kΩ). The EIA-96 system allows 96 distinct precision values per decade, matching the E96 preferred value series exactly.
What does the letter R mean on an SMD resistor?
The letter R marks the position of the decimal point in resistance values below 10 Ω, replacing the standard multiplier-digit structure. 4R7 = 4.7 Ω; R47 = 0.47 Ω; R100 = 0.100 Ω (100 mΩ); R001 = 0.001 Ω (1 mΩ). Current-sense shunt resistors in the milliohm range use this notation extensively. When you see R-notation on a 2010 or 2512 package, assume it’s a power-rated shunt application and check the current rating before substituting with a standard 0402 or 0603 value.
Can SMD resistors be customized for tighter tolerance or specific TCR requirements?
Yes. Beyond standard 5% and 1% catalog parts, manufacturers offer precision thin-film resistors with tolerances down to ±0.01% and TCR as low as ±5 ppm/°C for metrology-grade applications. Custom resistance values outside E96 preferred values, specific TCR matching between pairs (for ratio-critical circuits), and AEC-Q200-qualified versions with full lot traceability are available with lead times typically of 4–8 weeks. For volume procurement, it’s worth confirming that your distributor can provide the manufacturer’s qualification data and full material traceability documentation.
Conclusion
Zero-ohm jumpers are marked 0, 00, 000, or 0000 and have a defined current rating — they are not infinite-current shorts. Unmarked parts (common in 0201 and 01005) require reel label documentation and LCR meter verification. The single most important habit: verify any value marked “100” with a meter before assuming it’s 100 Ω — it’s 10 Ω.
Find What You Need on LCSC
LCSC Electronics stocks millions of SMD resistors across every package size, tolerance grade, and marking system — from general-purpose 0402 thick-film resistors at ±5% tolerance to precision 0603 thin-film parts at ±0.1% with EIA-96 markings, AEC-Q200-qualified automotive resistors with full lot traceability, and milliohm current-sense shunts in 2010 and 2512 packages with R-notation values. Whether you need a reel of 4.7 kΩ 0402 pull-ups for a digital interface, matched-pair 0.1% resistors for a precision voltage divider, or a low-TCR (±10 ppm/°C) thin-film resistor for an analog feedback loop, LCSC’s parametric search filters by resistance value, package size, tolerance, TCR, power rating, and AEC-Q200 qualification status in seconds. Every listing includes the manufacturer datasheet with full marking and footprint data. With real-time stock, competitive pricing from cut-tape prototype quantities to full reels, and global shipping, LCSC is where engineers go to source resistors reliably. Start at lcsc.com.
