SMD Resistor Code Calculator
Select the code type (3-digit, 4-digit or EIA-96) and enter the code printed on the SMD resistor to find its resistance value and tolerance.
Reviewed by the ToolNestr Editorial Team — July 2026
What different SMD package sizes mean
Package size determines power handling and suitability for different PCB assembly processes.
PCB Assembly Tech
Verify resistor values during board assembly and rework without needing to desolder and measure each component.
Electronics Repair
Quickly identify unknown SMD resistors on circuit boards during troubleshooting and repair work.
Circuit Designer
Choose the correct SMD resistor code format for your BOM and ensure pick-and-place machines get the right components.
Hobbyist
Decode SMD resistor markings on salvage boards and understand the values when building your own circuits.
| Package | Dimensions (mm) | Power rating | Typical marking | Best for |
|---|---|---|---|---|
| 0201 | 0.6 × 0.3 | 1/20 W | EIA-96 only | Smartphones, wearables |
| 0402 | 1.0 × 0.5 | 1/16 W | EIA-96 / 3-digit | Compact PCBs |
| 0603 | 1.6 × 0.8 | 1/10 W | 3-digit / 4-digit | General purpose |
| 0805 | 2.0 × 1.25 | 1/8 W | 3-digit / 4-digit | Prototyping, through-hole replacement |
| 1206 | 3.2 × 1.6 | 1/4 W | 3-digit / 4-digit | LED current limiting |
| 1210 | 3.2 × 2.5 | 1/2 W | 3-digit / 4-digit | Higher power circuits |
| 2010 | 5.0 × 2.5 | 3/4 W | 4-digit only | Power supplies |
| 2512 | 6.3 × 3.2 | 1 W | 4-digit only | High-power sensing |
| EIA-96 code | Value | Multiplier letter | Multiply by | Example |
|---|---|---|---|---|
| 01 | 100 | Z | ×0.001 | 01Z = 0.1 Ω |
| 10 | 124 | Y | ×0.01 | 10Y = 1.24 Ω |
| 25 | 178 | R | ×0.1 | 25R = 17.8 Ω |
| 50 | 324 | A | ×1 | 50A = 324 Ω |
| 68 | 499 | B | ×10 | 68B = 4.99 kΩ |
| 75 | 590 | C | ×100 | 75C = 59 kΩ |
| 96 | 976 | D | ×1000 | 96D = 976 kΩ |
How to use the SMD Resistor Code Calculator
Select the code type
Choose between 3-digit, 4-digit or EIA-96 format based on the marking printed on your SMD resistor.
Enter the code
Type the alphanumeric code exactly as printed on the resistor. Use uppercase letters. Letters R, Y, Z, etc. are handled automatically.
Read the decoded value
The calculator displays the resistance value with appropriate units, tolerance, and the EIA series the code belongs to.
Tips for reading SMD resistor codes
Use magnification for small packages
0402 and smaller packages have markings that are extremely difficult to read with the naked eye. Use a jeweler’s loupe or microscope to read the code accurately.
Check orientation before reading
SMD resistors can be placed in any orientation on the board. Rotate the board or use a magnifier to find the correct orientation of the printed code — it may be upside down.
Verify with a multimeter when possible
Codes can be ambiguous or damaged. If the code is unclear or the reading seems off, use a multimeter to measure the actual resistance value.
Watch for special markings
Zero-ohm jumpers are marked with a single “0” or “000”. Some manufacturers use proprietary codes or omit markings on the smallest packages. When in doubt, consult the datasheet.
How 3-digit codes work
The 3-digit code format uses two significant figures and one multiplier: ABC = AB × 10C. For example, code 471 means 47 × 101 = 470 Ω. Code 333 means 33 × 103 = 33,000 Ω = 33 kΩ. Values below 10 Ω use R as a decimal: 4R7 = 4.7 Ω. Zero-ohm jumpers are marked 000. This format is typically \u00b15% tolerance (E24 series).
How 4-digit codes work
The 4-digit code format uses three significant figures and one multiplier: ABCD = ABC × 10D. For example, code 1002 means 100 × 102 = 10,000 Ω = 10 kΩ. Code 5623 means 562 × 103 = 562,000 Ω = 562 kΩ. Values below 100 Ω use R: 10R0 = 10.0 Ω. This format provides higher precision and is typically \u00b11% tolerance (E96 series).
How EIA-96 codes work
The EIA-96 standard uses a two-digit code (01–96) followed by a letter (Z, Y, R, X, S, A, H, B, C, D, E, F). The two digits encode a three-digit significant figure value from the E96 series, and the letter encodes the multiplier. For example, code 01A decodes to 100 × 1 = 100 Ω, and code 96D decodes to 976 × 1000 = 976,000 Ω = 976 kΩ. This compact format fits on tiny 0201 and 0402 packages while maintaining \u00b11% precision.
R notation explained
The letter R in SMD codes functions as a decimal point. In 3-digit codes: 4R7 = 4.7 \u03a9, 0R22 = 0.22 \u03a9, R100 = 0.100 \u03a9. In 4-digit codes: 10R0 = 10.0 \u03a9, 0R100 = 0.100 \u03a9. This notation avoids ambiguity when printing tiny decimal points on small components and is commonly used for low-value precision resistors.
Worked examples
Frequently asked questions
How do 3-digit SMD resistor codes work?
In a 3-digit code, the first two digits are significant figures and the third digit is the multiplier (power of 10). For example, 472 means 47 × 10² = 4700 Ω = 4.7 kΩ. A value of 0 or 000 indicates a zero-ohm jumper resistor.
How do 4-digit SMD resistor codes work?
In a 4-digit code, the first three digits are significant figures and the fourth digit is the multiplier. For example, 1002 means 100 × 10² = 10000 Ω = 10 kΩ. Four-digit codes are used for 1% tolerance resistors with higher precision.
What is the EIA-96 code system?
EIA-96 is a standard for 1% SMD resistors where a two-digit code (01 to 96) represents a specific resistance value, followed by a letter representing the multiplier. For example, 01Y = 100 Ω × 0.01 = 1 Ω. This allows compact marking of precision resistors on small packages.
What does the letter R mean in SMD codes?
The letter R represents a decimal point in 3-digit and 4-digit codes. For example, 4R7 means 4.7 Ω, and 0R22 means 0.22 Ω. This is commonly used for low-value resistors where a decimal point would be hard to read on small components.
What are the common SMD resistor package sizes?
Common package sizes include 0201 (0.6 × 0.3 mm), 0402 (1.0 × 0.5 mm), 0603 (1.6 × 0.8 mm), 0805 (2.0 × 1.25 mm), 1206 (3.2 × 1.6 mm), 1210 (3.2 × 2.5 mm), 2010 (5.0 × 2.5 mm), and 2512 (6.3 × 3.2 mm). Larger packages can dissipate more power.
What is the power rating of SMD resistors?
Power ratings vary by package: 0201 = 1/20W, 0402 = 1/16W, 0603 = 1/10W, 0805 = 1/8W, 1206 = 1/4W, 1210 = 1/2W, 2010 = 3/4W, 2512 = 1W. These ratings assume adequate PCB copper area for heat sinking.
How do I read an SMD resistor marked with only a number?
If the marking is a 2-digit code, it is likely an EIA-96 code (for 1% resistors) or a special marking. If it is 3 or 4 digits, use the standard digit + multiplier system. If it has an R, treat R as the decimal point.
What is the tolerance of SMD resistors?
Tolerance varies: 3-digit codes typically indicate ±5% tolerance, 4-digit codes indicate ±1%, and EIA-96 codes indicate ±1%. Some specialty resistors use ±0.5%, ±0.25%, or ±0.1% tolerances, usually with additional markings.
How do I identify the value of an SMD resistor with a multimeter?
Set your multimeter to resistance mode and measure across the resistor terminals. For in-circuit measurements, be aware that other components can affect the reading. Out-of-circuit measurements are always more reliable.
Why are SMD resistors marked with codes instead of color bands?
SMD resistors are too small for color bands. The tiny packages use alphanumeric codes because they can be printed with high precision and read under magnification. The code system is standardized by EIA and JEDEC.
Sources & references
This tool uses standard formulas and reference values from:
- • NFPA 70 — National Electrical Code (NEC), conduit fill, box fill and conductor ampacity. nfpa.org
- • IPC-2221, Generic Standard on Printed Board Design (trace width / current). ipc.org
- • NIST reference constants and unit definitions; IEEE standards where applicable. nist.gov
For educational and preliminary use. Verify against full engineering calculations and the governing standard before any real design.