SMD Resistor Calculator: Decode and Encode Markings

How to use the smd resistor code calculator

1. Select Decode to read a marking, or Encode to generate one.
2. For decoding, type the SMD resistor code (for example 103, 4R7 or 01C).
3. For encoding, enter the resistance in ohms and choose 3-digit, 4-digit or EIA-96 format.
4. The result updates instantly with the resistance in ohms and a human-readable value using kΩ or MΩ where appropriate.

How 3-digit and 4-digit SMD codes work

A standard smd resistor code uses digits to represent significant figures followed by a multiplier exponent. In the 3-digit system the first two digits are the significant figures and the third digit is the power of ten. For example, the code 103 means 10 multiplied by 10³, which equals 10,000 ohms or 10 kΩ.

The 4-digit system works the same way but uses three significant figures and a fourth multiplier digit. The code 1002 means 100 multiplied by 10², giving 10,000 ohms. Four-digit codes are often used on 1 percent precision parts.

When the letter R appears in the marking it replaces the decimal point rather than acting as a multiplier. The code 4R7 therefore means 4.7 ohms, and R047 means 0.047 ohms (47 milliohms). A code of all zeros (000 or 0000) designates a zero-ohm jumper used as a wire link on the PCB. Multiplier digits 8 and 9 are rarely used and differ between manufacturers, so the calculator does not decode them.

Common SMD resistor codes reference

This table lists frequently encountered smd resistor markings and their decoded values. Use it as a quick lookup alongside the calculator above.

Encoding resistance values to SMD codes

To go from ohms back to a marking, the process reverses. First decide whether you need a 3-digit or 4-digit code. Express the resistance with two significant digits (for 3-digit) or three significant digits (for 4-digit). The exponent becomes the last digit of the code.

For example, 4,700 ohms is 47 times 10². Using 3-digit format the significant figures are 47 and the multiplier is 2, producing the code 472. If the value is less than 10 ohms, use R as the decimal point: 0.47 ohms becomes R47, and 4.7 ohms becomes 4R7. In 4-digit format the same two values become R470 and 4R70.

Not every arbitrary resistance can be represented exactly with these formats because only two or three significant digits are available. Standard E12 and E24 series values map cleanly. For anything else the calculator picks the nearest code, shows what that code actually decodes to, and tells you it was rounded.

EIA-96 codes for 1 percent resistors

Small precision resistors, typically 1 percent parts in 0402 and 0603 sizes, often use the EIA-96 marking: two digits followed by a letter, for example 01C. The two digits (01 to 96) are an index into the 96 values of the E96 series, which have three significant figures, and the letter is the multiplier. This smd resistor calculator decodes these codes and can encode any standard E96 value.

For example, 01C is index 01 (100) times 100, which is 10 kΩ, and 68C is index 68 (499) times 100, which is 49.9 kΩ. The multiplier letters are:

The index table below lists the base value for every code from 01 to 96.

A marking such as 47R is ambiguous. Printed on a larger resistor it normally means 47 ohms, but it is also a valid EIA-96 pair (index 47 is 301, R is times 0.01, so 3.01 ohms). The calculator reports the 47 ohm reading first and shows the EIA-96 reading as an extra row; check the part size and datasheet to decide.

Practical tips for reading SMD markings

SMD components are tiny, and the printed smd resistor marking can be hard to read without magnification. A jeweller's loupe or a USB microscope makes identification much easier. Be careful not to confuse the letter R with a poorly printed digit; in a numeric code it always acts as a decimal point.

The marking never includes the tolerance. Three-digit codes are usually found on 5 percent parts and EIA-96 or four-digit codes on 1 percent parts, but that is a convention, so measure with a meter if the value matters. For through-hole resistors with colour bands, use the resistor color code calculator instead, and for the current and voltage that a value implies, try the Ohm's law calculator.

Zero-ohm jumpers marked 000 or 0000 look identical to resistors but serve as simple wire links. They are used to route traces across each other on single-layer boards or to configure optional circuit paths during manufacturing.

Worked examples