Decode resistor color bands into an ohm value, or calculate total resistance for resistors in parallel or series.
On a 4-band resistor, the first two bands are significant digits, the third is a multiplier (a power of ten to multiply by), and the fourth is tolerance. A 5-band resistor adds a third significant digit for extra precision before the multiplier and tolerance bands.
Resistors in series simply add up: Rtotal = R1 + R2 + …. Resistors in parallel combine differently, since current splits between them: 1/Rtotal = 1/R1 + 1/R2 + … — the total is always less than the smallest individual resistor.
Start from the side where the bands are closer together, or where the tolerance band (often gold or silver) is clearly separated at the opposite end — that separated band is always read last.
A resistor with only 3 significant/multiplier bands and no separate tolerance band is assumed to have a ±20% tolerance, per the standard convention — not covered by this calculator's band-count options.
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