Resistor Calculator

Calculate resistor values, color codes, and series/parallel resistance combinations.

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About the Resistor Calculator

This calculator computes resistance values for series and parallel circuits and decodes resistor color bands. You get the total resistance in ohms, plus the value and tolerance behind any color code you enter.

For a series connection it applies the standard formula R_total = R1 + R2 + ... + Rn, which adds every value directly. For a parallel pair it uses R_total = (R1 × R2) / (R1 + R2). You enter individual resistor values in ohms or the band colors of a marked resistor. Tip: hold the resistor with the gold or silver tolerance band on the right before reading the other bands.

  • Choose a mode: color code decoding or series and parallel combination.
  • Enter the band colors or the resistor values in ohms.
  • Read the output showing the resistance, tolerance, or combined total.