How to use the SMD resistor code calculator
- Choose Code → value, then type the marking printed on the resistor — for example
472,1002,4R7,R22,01Cor68X. Capital or small letters both work. - Read the resistance, the code type and a tolerance hint. The calculator also shows how the code is worked out, step by step.
- Choose Value → code to go the other way: type a value such as 4.7 kΩ and see every marking it could carry (3-digit, 4-digit and EIA-96).
- Open the EIA-96 table at the bottom to see all 96 codes. The code you typed is highlighted.
The four SMD marking systems
| Format | Example | How to read it | Typical tolerance |
|---|---|---|---|
| 3-digit | 472 | 47 × 10² = 4.7 kΩ | ±5% |
| 4-digit | 1002 | 100 × 10² = 10 kΩ | ±1% |
| R-notation | 4R7, R22, 47R | R is the decimal point: 4.7 Ω, 0.22 Ω, 47 Ω | ±5% (3 characters), ±1% (4 characters) |
| EIA-96 | 01C, 68X | value from table × letter multiplier | ±1% |
| Zero-ohm link | 0, 000 | a jumper, not a real resistor | — |
Formula
The EIA-96 multiplier letters are:
| Letter | Multiplier | Letter | Multiplier |
|---|---|---|---|
| Z | × 0.001 | B or H | × 10 |
| Y or R | × 0.01 | C | × 100 |
| X or S | × 0.1 | D | × 1,000 |
| A | × 1 | E | × 10,000 |
| F | × 100,000 |
The two digits of an EIA-96 code are not the value itself — they are a position in the E96 list. Code 01 is 100, 02 is 102, 03 is 105 … 68 is 499 … 96 is 976. That is why the table is needed.
Which tolerance does a code mean?
The marking style gives a good hint. 3-digit codes are normally used for ±5% parts from the E24 series, while 4-digit and EIA-96 codes are used for ±1% precision parts. The marking does not prove the tolerance, though — if it matters, check the reel label or datasheet.
Common mistakes
- Reading the code upside down. SMD parts are tiny and can be rotated. If a value is not a standard one, turn the board and read again.
- Confusing resistors with capacitors. Ceramic capacitors are usually unmarked, but some parts with 3-digit codes are capacitors (in pF) or inductors. Black body with white text is usually a resistor. Decode capacitor markings with the capacitor code calculator.
- Treating EIA-96 digits as the value. 68X is not 6.8 Ω — it is 499 × 0.1 = 49.9 Ω.
- Expecting a marking on 0402 parts. Very small resistors are usually blank.
Related tools
Need a value you do not have? Combine two resistors with the series and parallel resistor calculator. For through-hole parts with colour bands, use the resistor colour code calculator. Sizing an LED resistor? Try the LED resistor calculator. New to circuits? Start with Ohm's law explained with examples and our breadboard basics guide, then practise with one of our electronics kits.
