The method

Separate the digits from their roles

Bandvalue interprets ordered color names that you select manually. Four-band mode uses two significant digits, then a multiplier and tolerance. Five-band mode uses three significant digits, then multiplier and tolerance. Changing the mode changes those roles. The hidden third-digit control has no effect in four-band mode.

A named manufacturer reference

The mapping is the declared Vishay reference convention from document 20143, whose returned page is marked revision 28 Aug 2009, corroborated by Vishay chart 49411. This page does not assert that a dated chart is the latest universal standard or that every manufacturer uses an identical marking family.

Digits are black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8 and white 9. In this subset the first digit must be brown through white. A leading black selection and zero-ohm-link interpretation are unsupported; this is a tool boundary, not a verdict about every physical marking.

Multiplier and tolerance

Black through white multipliers represent powers of ten from 10^0 through 10^9. Gold is ×0.1 and silver is ×0.01. Tolerance choices are brown 1%, red 2%, green 0.5%, blue 0.25%, violet 0.1%, gray 0.05%, gold 5% and silver 10%. Gray is shown as “gray (grey)” in controls; 0.05% is specifically this reference table's mapping.

Exact arithmetic

Join the significant digits to form S and take multiplier exponent e. The nominal resistance is R = S × 10^e ohms. For marked tolerance t percent, the arithmetic interval is R × (1 − t/100) through R × (1 + t/100). This is a reference interval, not a measurement or a temperature, aging or circuit-behavior model.

The script uses integer-scaled BigInt arithmetic. Let C = S × 10^(e + 2) centiohms, and let b be tolerance in basis points of nominal resistance. Nominal microohms are C × 10000. Lower and upper microohms are C × (10000 − b) and C × (10000 + b). Divide those integers by 1,000,000 to display exact ohms. For example, 100 basis points means 1% and five means 0.05%. No binary floating rounding drives the result.

A worked default

Yellow, violet, red, gold in four-band mode gives digits 47, multiplier 100 and nominal 4700 Ω. Gold marks ±5%, so the arithmetic interval is 4465 to 4935 Ω. The diagram illustrates only your selected order, with the role and color name also written outside it.

Supported subset and limits

Only the active four or five named bands are read. No six-band temperature coefficient, absent-tolerance code, SMD/EIA96 code, military or fuse marks, body-end-dot marking, preferred-series search or inverse color generation is included. Supported combinations do not establish that a component is manufactured, correctly identified or in this code family. Physical direction and uncertain color recognition remain outside the calculation.

The smallest supported four-band nominal is 0.1 Ω and the largest five-band nominal is 999,000,000,000 Ω. Displayed decimals remain exact. Every edit clears old results and exports until you decode again. Startup and reset restore the fixed example; no camera, network service or measurement device is used.