SMD Resistor Code Calculator (3-Digit, 4-Digit & EIA-96)
Convert the numeric marking printed on a surface-mount (SMD) chip resistor into a resistance value. Supports 3-digit codes, 4-digit codes (precision resistors), and EIA-96 codes (2 digits plus a letter), with the format auto-detected from your input.
Tips
- 3-digit codes are common on general-purpose SMD resistors (typically ±5% tolerance), while 4-digit codes tend to appear on precision resistors rated ±1% or tighter. The digit count alone gives you a rough sense of precision.
- An EIA-96 code packs one extra significant digit (three digits of precision) into just two numeric characters, letting even tiny chip resistors carry a high-precision printed value.
- "Auto-detect" guesses the format from the length and character types of your input (digits only vs. ending in a letter). If the guess doesn't match what you intended, pick the format explicitly from the dropdown.
- A 0Ω jumper resistor is usually marked "000" or "0" rather than a real resistance code — while "000" can technically be parsed as a 3-digit code, it's really a special marking meaning "connect this trace directly."
- When reading a code under a loupe or microscope, worn printing can make similar characters like 0/D or 1/I hard to tell apart — checking from a couple of angles helps avoid misreads.
Frequently Asked Questions
Side Note — Ever-Shrinking Resistors and Their Marking Tricks
As electronic components have gotten smaller and smaller, resistors have moved to surface-mount (SMD) packaging at an accelerating pace. The colored bands used on a traditional leaded resistor simply won't fit on the surface of a chip just a few millimeters across, which is why short marking codes made of digits (and occasionally letters) were introduced instead.
The 3-digit and 4-digit codes are essentially the color-code idea translated straight into numbers, but the EIA-96 code takes things a step further. By preparing a standardized lookup table in advance, two numeric digits alone can express 96 possible significant-figure values (effectively three digits of precision), with the numeric part acting purely as an "index" into that table. This saves printing space while matching the precision of a 4-digit code.
In recent years, even tinier packages such as 0402 (0.4 mm × 0.2 mm) and 0201 chip resistors have become common, and an increasing number of these parts skip printing altogether (unmarked resistors). In that case you have to identify the resistance from the tape-and-reel label or reel part number instead, so visual identification via a marking code is likely to remain limited to parts above a certain size going forward.