Repair technicians on Delhi's Gaffar Market or Chennai's Ritchie Street read surface-mount resistors under a lamp all day. Beginners usually stumble over the same few codes. Learning how to read SMD resistor codes takes about ten minutes: there are only three systems, and each follows one simple rule.
1. Three-digit codes (usually ±5%)
The first two digits are the value; the third is the number of zeros to add.
| Code | Read as | Value |
|---|---|---|
| 472 | 47 + 00 | 4,700 Ω = 4.7 kΩ |
| 103 | 10 + 000 | 10 kΩ |
| 220 | 22 + (no zeros) | 22 Ω |
| 105 | 10 + 00000 | 1 MΩ |
Why is 100 only 10 ohms?
Because it is 10 followed by zero zeros. It's one of the most common mix-ups on the bench; 101 is 100 Ω and 102 is 1 kΩ.
2. Four-digit codes (usually ±1%)
The first three digits are the value; the fourth is the number of zeros. 4702 = 470 + 00 = 47 kΩ; 1001 = 100 + 0 = 1 kΩ; 2201 = 2.2 kΩ.
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3. The letter R
R marks the decimal point in low values: 4R7 = 4.7 Ω, R22 = 0.22 Ω, 0R5 = 0.5 Ω. These usually appear on current-sense and low-value resistors near power circuits.
4. EIA-96 codes (±1%, small parts)
Tiny 0603 resistors don't have room for four digits, so they use two digits and a letter. The two digits are an index into the E96 value table (01 = 100, 02 = 102, … 96 = 976), and the letter is the multiplier.
| Letter | Multiplier | Example |
|---|---|---|
| X or S | × 0.1 | 68X = 49.9 Ω |
| A | × 1 | 01A = 100 Ω |
| B or H | × 10 | 01B = 1 kΩ |
| C | × 100 | 01C = 10 kΩ |
| D | × 1,000 | 01D = 100 kΩ |
5. Zero-ohm parts
0, 00 or 000 marks a zero-ohm resistor: a jumper link on the board, used to bridge tracks or select options.
Bench tips
- Light and magnification: 6/9 and 1/7 are easy to confuse on 0402 and 0603 parts.
- Orientation: if a code reads upside-down, it may make sense the other way round.
- Unmarked parts: 0402 and smaller often carry no code; measure out of circuit.
- In-circuit readings are misleading: other components in parallel lower the measured value.
How to read SMD resistor codes: which system is it?
Three printed digits (472) mean the 3-digit system; four digits (4702) the 4-digit system; a letter R anywhere (4R7) means a decimal point; and two digits followed by a letter (01C) mean EIA-96. Once the system is clear, the value is one step away.
The SMD resistor calculator decodes 3-digit, 4-digit, R-decimal and EIA-96 codes instantly; type the code exactly as printed.
Frequently asked questions
How do I read a 3-digit SMD resistor code?
First two digits are the value, the third is the number of zeros. 472 = 4.7 kΩ.
How do I read a 4-digit SMD code?
First three digits are the value, the fourth the number of zeros. 4702 = 47 kΩ.
What does R mean on an SMD resistor?
It marks the decimal point: 4R7 is 4.7 Ω.
What is an EIA-96 code?
A two-digit index into the E96 value table plus a multiplier letter, used on small 1% resistors.
What does 000 on a resistor mean?
It is a zero-ohm jumper link.
Keep reading
- SMD Resistor Calculator: the free tool this guide explains.
- All math & utility calculators
- PTR PTS Margin for Chemists: Markup vs Margin, With Examples
Sources: IEC 60062 marking codes; EIA-96 code table.