Free Resistor Color Code Calculator – 4-Band and 5-Band

Decoding 4-Band and 5-Band Resistor Colours

Resistors are marked with coloured bands because they are far too small to carry a printed number reliably. This calculator turns those bands back into a value, handling both 4-band and 5-band resistors according to the IEC 60062 standard. Each colour stands for a digit, a multiplier, or a tolerance, and once you know the pattern you can read any resistor — but the tool does it instantly and removes the risk of misreading a faded band. Pick the band count, choose each colour, and you get the resistance, the tolerance, and the guaranteed value range. The decoding rule is positional. On a 4-band resistor the first two bands are significant digits, the third is a multiplier (a power of ten), and the fourth is the tolerance. In words, resistance equals the two-digit number formed by the first two bands, multiplied by ten raised to the multiplier band's value. A 5-band resistor simply inserts a third significant digit before the multiplier for extra precision. The colour-to-number map is the one every electronics student memorises: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. For multipliers, gold means ×0.1 and silver ×0.01; for tolerance, gold is ±5 percent and silver ±10 percent. Here is a worked example. Take a 4-band resistor coloured brown, black, red, gold. Brown is 1 and black is 0, giving the significant figures 10. Red as a multiplier means ×10², or ×100, so the resistance is 10 × 100 = 1,000 ohms, which reads as 1 kΩ. The gold tolerance band means ±5 percent, so the true value is guaranteed to fall between 950 and 1,050 ohms. The calculator shows all of this at once, choosing the most readable unit automatically. Two more passes confirm the pattern. Yellow, violet, orange, gold gives digits 47 with a ×10³ multiplier, so 47 × 1,000 = 47,000 ohms, or 47 kΩ, with a ±5 percent window of 44,650 to 49,350 ohms. Red, red, brown, gold is far humbler: digits 22 with a ×10 multiplier, giving just 220 ohms — the resistor you reach for most often in beginner LED circuits. That makes it genuinely handy when sorting a parts bin, repairing a board, or confirming a resistor before you solder it in, particularly when age or heat has dulled the colours. Seeing the min and max range matters in precision circuits where a value near the edge of tolerance could shift a filter or timing constant. Three specific moments where it earns its place: a student building a first breadboard circuit checks that the resistor they grabbed really is 220 ohms and not 22 kΩ before powering up. A repair technician pulling a suspect resistor from a scorched board decodes brown, black, green, gold as 1 MΩ and confirms the schematic against a part whose colours have browned with heat. Someone who has just tipped four bags of loose resistors into one drawer uses it to re-sort them, since 3,300 ohms (orange, orange, red, gold) and 33,000 ohms differ by only one band. One reliable tip for reading direction: the tolerance band usually sits slightly apart from the rest, and a gold or silver band almost always marks the tolerance end, so start from the opposite end. Read a resistor backwards and you get a wildly different value: brown, black, red the wrong way round becomes red, black, brown, or 200 ohms instead of 1,000. When the colours are genuinely ambiguous, and heat-darkened red versus brown is the usual culprit, stop guessing and measure with a multimeter; the printed bands are the manufacturer's claim, the meter is the fact. Keep in mind the tolerance too: a ±5 percent 1 kΩ part is only promised to sit between 950 and 1,050 ohms, so do not blame the calculator when your meter reads 1,032. Every lookup uses the standard band tables built into the tool, and all decoding runs locally in your browser so nothing you enter is uploaded.

Resistor Color Code Calculator Formula & Method

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