The four SMD marking systems
Surface-mount resistors are too small for color bands, so they carry printed codes instead — in one of four schemes:
- 3-digit — two significant figures then a power-of-ten multiplier.
472= 47 × 10² = 4.7 kΩ.100= 10 × 10⁰ = 10 Ω. - 4-digit — three significant figures then the multiplier, for
tighter tolerances.
4702= 470 × 10² = 47 kΩ. - R-notation — an
Rstands in for the decimal point on sub-10 Ω parts.4R7= 4.7 Ω,R047= 0.047 Ω. - EIA-96 — two digits index the E96 table, a letter gives the
multiplier.
01C= 100 × 100 = 10 kΩ. Used on 1% parts where three-figure precision won't fit in three characters.
Telling 3-digit from EIA-96
Both are three characters, but EIA-96 always ends in a letter while
the 3-digit code is all numbers. So 22A is EIA-96
(165 Ω), whereas 220 is 22 Ω (3-digit). A single 0
(or 000) marks a zero-ohm jumper.
EIA-96 multiplier letters
| Letter | Multiplier | Letter | Multiplier |
|---|---|---|---|
| Z | 0.001 | B / H | ×10 |
| Y / R | 0.01 | C | ×100 |
| X / S | 0.1 | D | ×1 000 |
| A | ×1 | E | ×10 000 |
| F | ×100 000 |
Frequently asked questions
- What does an underline under the code mean?
- It's just an orientation/legibility aid on codes that could be read
upside down (like
81vs18) — it doesn't change the value. - When does the EIA-96 code appear?
- Only when the value lands exactly on an E96 (1%) figure. 1 kΩ is E96
value 100 with a ×10 multiplier, so its EIA-96 marking is
01B; a non-E96 value like 4.7 kΩ has no EIA-96 form and shows only the 3-digit code. - Need the through-hole color bands instead?
- Use the resistor color code calculator for banded axial resistors.