Resistor Color Code
Calculates or decodes value, tolerance and color bands of a resistor (4, 5 or 6 bands).
4.7 kΩ
4.465 kΩ – 4.935 kΩ
Why 4, 5 and 6 bands represent different amounts of precision
A 4-band resistor has 2 significant digits (e.g. "47" × multiplier) — typically ±5% or ±10% precision, enough for most circuits. A 5- or 6-band one has 3 significant digits (e.g. "470" × multiplier), allowing tighter tolerances (±1% or better) — the extra digit band only pays off with a tighter tolerance too; a 3-digit resistor at ±10% wouldn't make sense in practice. The 6th band (6-band resistors only) adds no value precision at all — it states the temperature coefficient (how much the resistance drifts per degree Celsius), relevant only in circuits sensitive to temperature variation.
Why resistors come in "odd" values (the E12/E24 series)
Commercial resistors don't exist in every possible value — they come from standardized series (E12, E24, E96...) spaced logarithmically, not linearly, from one value to the next. The E12 series (12 values per decade, ±10% tolerance) includes 47Ω but not 48Ω; the E24 series (24 values per decade, ±5%) fills the gap with more options, but still follows the same logarithmic spacing — the idea is that, accounting for each resistor's tolerance, the real value range covered by one nominal value already touches the next one's range, without wasting manufacturing on redundantly close values. That's why practically every published circuit uses values like 220Ω, 4.7kΩ, 10kΩ — not because they're "round", but because they belong to a real E12/E24 series you can actually buy.
Frequently asked questions
Very old 3-band resistors (just 2 digits and a multiplier) had no tolerance band of their own — ±20% was the standard manufacturing tolerance back then, so the physical absence of a fourth colored band already communicated that. This tool offers "No band" as an explicit tolerance option for the same reason, even though it always works with 4, 5 or 6 bands.
Because neither one follows from the resistance value alone — two resistors of exactly 4.7 kΩ can have very different tolerances (±5%, ±1%, ±0.1%...) depending on how they were made. This tool asks for both separately, never assuming a silent default that could be wrong for the real resistor you're trying to build or buy.
Because not every value fits exactly into 2 or 3 significant digits — e.g. 4321 Ω at 4 bands (2 digits) becomes 4300 Ω, the closest representable value. Switching to 5 or 6 bands (3 digits) represents the value more precisely.
The typical precision: 4 bands (2 digits) for ±5%/±10%/±20% tolerances, the standard for general consumer electronics; 5 bands (3 digits) for tighter tolerances, common in precision analog circuits; 6 bands adds the temperature coefficient, relevant only when value stability across temperature matters (e.g. precision instrumentation).
IEC 60062 reserves Gold and Silver for two specific roles — multiplier (×0.1 and ×0.01, for resistors under 10 Ω) and tolerance (±5% and ±10%) — never as a significant digit (0-9), a role reserved for the ten colors from Black to White.
No — a deliberate scope decision for this version. 3-band resistors (with no tolerance band of their own) are rare today; when found, entering the tolerance as "No band" in this tool (±20%) already covers the case. The Pink color (×0.001), added to IEC 60062 in 2016 for shunt resistors under 1 mΩ, is a fairly specialized application, out of scope for this first version.
Nexinon Principles
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