SMD resistor codes.

How the three systems work

Quick rule of thumb: count digits and check for letters. Three numbers = general purpose (5%); four numbers = precision (1%); two numbers + letter = EIA-96 (1%, compact).

Reading 3-digit codes

The first two digits are the significant figures; the third is the multiplier (power of 10).

Watch out: 100 means 10 Ω (10 × 10⁰), not 100 Ω. The trailing zero is the multiplier, not the third significant digit.

Reading 4-digit codes (precision)

First three digits are significant figures; fourth is the multiplier. Used for ±1% E96 series.

EIA-96 multiplier letters

The third character of an EIA-96 code is a letter giving the multiplier:

In practice, A, B, C, X cover 99% of what you'll see. The duplicates (Y/R, X/S, B/H) come from harmonizing different national standards.

EIA-96 base value table (codes 01–96)

The first two digits of an EIA-96 marking look up a base value in this table (E96 series, ±1% standard values):

Worked EIA-96 examples

Quick reference: common values

Package sizes and what you'll see on each

Common pitfalls

• 100 ≠ 100 Ω. In the 3-digit system, 100 is 10 × 10⁰ = 10 Ω. The 3rd digit is the multiplier. For 100 Ω, the marking is 101.
• 3-digit and 4-digit codes look similar. A part marked 1001 on an 0805 (4-digit, 1 kΩ) and 101 on an 0603 (3-digit, 100 Ω) can be confused if you don't count digits. When in doubt, measure.
• Underlined codes are precision E24 in some manufacturer schemes. A 122 (underlined middle digit) or a single underbar may mean precision (1% or better) at an E24 value not normally in the precision series. Convention varies by maker.
• Zero-ohm jumper markings vary. Single 0, 00, 000, or 0000 all indicate a wire bridge, not a 0 Ω calculation. Don't try to decode them.
• Tolerance and tempco aren't on the marking. The code gives resistance only. For 1%, 0.1%, 0.01% variants or for low-tempco precision parts, you need the manufacturer's reel label or BOM.
• Power rating is in the package, not the code. An 0603 part marked 103 (10 kΩ) is rated about 0.1 W; a 1206 with the same 103 marking is rated 0.25 W. Same value, very different power handling.
• 0402 and smaller usually have no marking. Below 0603 there's typically no room to print legible characters. The only way to identify the part is from the assembly BOM, the reel label, or a multimeter.
• "R" on a non-EIA-96 code means decimal point. 4R7 = 4.7 Ω, R47 = 0.47 Ω. In EIA-96, R is also one of the multiplier letters (×0.01) — context determines which. If the code is exactly 3 characters with two digits and one letter at the end, it's EIA-96; otherwise R is a decimal point.

Common questions

How do I read an SMD marked '472'?

It's the 3-digit code: first two digits (47) are significant figures, third (2) is the power of 10 multiplier. So 472 = 47 × 10² = 4,700 Ω = 4.7 kΩ. This is one of the most common SMD resistor markings.

What if the resistor has 4 digits like '4701'?

That's the 4-digit precision code (typically ±1% E96 series). First three digits (470) are significant; fourth (1) is the multiplier. So 4701 = 470 × 10¹ = 4,700 Ω = 4.7 kΩ. Same value as '472' in the 3-digit code, but ±1% instead of ±5%.

Why does my SMD resistor say '01C' instead of digits?

It's EIA-96 code, used on tiny precision SMD resistors where there's no room for 4 digits. First two digits (01) look up a base value in the EIA-96 table (01 = 100). The letter (C) is a power of 10 multiplier (C = 100). So 01C = 100 × 100 = 10,000 Ω = 10 kΩ. All EIA-96 resistors are ±1% precision.

Why is my SMD resistor blank — no markings?

Below 0603 (1.6 × 0.8 mm) package size, there's typically no room for legible markings. 0402 and 0201 resistors often ship unmarked. The only way to identify them is from the PCB assembly drawing, manufacturer's reel label, or by measurement with a multimeter.

What does '0' or '000' on an SMD resistor mean?

Zero ohm — it's not a resistor but a jumper/bridge used in PCB layout. They look like resistors so automated assembly machines can place them like any other component, but their function is to connect traces (often for SKU variants or to cross-jump signals). Resistance is typically under 50 mΩ — effectively a wire.

Sources

• IEC 60062 — Marking codes for resistors and capacitors. The international standard underlying the EIA-96 numeric base values and tolerance letter codes.
• EIA-RS-279 — The EIA standard for resistor color and marking systems.
• E-series preferred values per IEC 60063 — E24, E48, E96, E192 series define which resistance values are standard at each tolerance class.

Disclaimer. Values shown are based on standardized marking conventions. Manufacturers occasionally use proprietary or hybrid schemes. For critical applications, confirm the value with a multimeter and consult the manufacturer's datasheet.

See also