Electronics Toolbox

SMT Resistor Code Calculator

Series Resistors

This calculator converts the 3-digit codes which are found on surface mount resistors.

Resistance =

How it works

Surface mount resistors utilise a three-digit coding system to denote their resistance values. Here's how the three-digit codes work:

  1. First Two Digits: These are the significant figures of the resistor's value. For example, in the code "473", the "47" represents the significant figures.

  2. Third Digit: This digit is the multiplier, indicating the power of ten by which to multiply the first two digits. For instance, in the code "473", the "3" means that the significant figures (47) should be multiplied by \(10^3\) (1000).

Thus, the resistor code "473" translates to 47,000 ohms, or 47 kilo-ohms.

Examples:

  • 104: This means 10 x \(10^4\) = 100,000 ohms (100 kOhms).
  • 220: This means 22 x \(10^0\) = 22 ohms.
  • 330: This means 33 x \(10^0\) = 33 ohms.
  • 471: This means 47 x \(10^1\) = 470 ohms.