Resistor Color Code Calculator
Decode 4-band and 5-band color codes into resistance, tolerance and range.
Brown = 1
Black = 0
Red = ×100
Gold = ±5%
1kΩ
±5% tolerance
value = digits × 10^multiplier · range = value ± tolerance%
EIA-RS-279 four- and five-band codes. A sixth band is the temperature coefficient and is not decoded here, and a three-band part has no tolerance band at all — that is ±20% by convention, not the figure this returns.
How it works
Choose 4-band or 5-band. Four bands carry two significant digits, five carry three — the third digit is why precision parts use five.
Set a color for each band, reading from the end the bands are crowded toward. The tolerance band is the one separated by a wider gap.
The digit bands form the significant figures, the multiplier band is the power of ten they are scaled by, and the last band is the tolerance.
The value, the tolerance and the resulting minimum and maximum update as each band changes. Every band is also shown decoded, so a misread band is visible rather than buried in the answer.
EIA-RS-279 color code
The first two bands — three on a 5-band part — are significant digits, the next is a power-of-ten multiplier, and the last is the tolerance. Gold and silver carry no digit and appear only as multiplier or tolerance bands; as multipliers they divide by 10 and 100, which is how the code reaches values below 10 Ω that two digits alone cannot express.
R = digits × 10^multiplier range = R ± tolerance%
Use cases
Identifying a part out of the bin
Brown-black-red-gold decodes to 1, 0, ×100 — 1 kΩ at ±5%. The same first two bands with an orange multiplier are 10 kΩ, which is the single most common misread on a board because brown, red and orange are one step apart on the ramp and look alike under a bench lamp.
Values below 10 Ω
Two digits stop at 99, so anything under 10 Ω needs a dividing multiplier. Green-blue-gold is 56 × 0.1 = 5.6 Ω, and brown-black-silver is 0.1 Ω — the current-sense range, where the tolerance band matters more than the value does.
Reading a 5-band precision part
Brown-black-black-brown-brown is 100 × 10 = 1 kΩ at ±1%, a range of 990 Ω to 1010 Ω. The fourth band on a 5-band part is the multiplier, not the tolerance; treating it as a 4-band code gives 100 Ω and a wrong answer that still looks plausible.
Checking a meter reading against the band
A part marked 4.7 kΩ ±5% is in spec anywhere from 4465 Ω to 4935 Ω. A meter showing 4.55 kΩ is therefore a good part, not a drifted one — the reading only becomes evidence of a fault once it leaves the range the bands allow.
Sanity-checking a decode against the E-series
Standard parts come from fixed series: E24 for ±5% (10, 11, 12, 13, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82) and E96 for ±1%. Decode a 5% part to 4.4 kΩ and the value itself is the error message, because no such part is made.
Bands too scorched to read
Heat browns a body until red and orange converge, and the code stops being evidence. Decode what you can see to bracket the value, then measure the part out of circuit — the color code is a label, and a resistor that has run hot enough to discolor may well be out of tolerance anyway.
Questions
- Which end is band one?
- The bands are grouped toward one end and the tolerance band sits alone across a wider gap, so read from the crowded end. Gold and silver never carry a digit, so a gold or silver band tells you which end is the tolerance end and therefore which end to start from.
- What about a sixth band?
- The sixth band is the temperature coefficient in ppm/°C — brown 100, red 50, orange 15, yellow 25, blue 10. It sits after the tolerance band and does not change the decode of the first five, so read a 6-band part here as a 5-band one and take the coefficient separately.
- Why can I not pick black or white for tolerance?
- Black, orange, yellow and white have no tolerance value assigned in the standard, so the tolerance picker only offers the eight colors that do. The same applies in reverse: gold and silver have no digit, so they never appear in a digit band.
- What about a resistor with only three bands?
- Three bands means no tolerance band, which is ±20% by convention. Read it as a 4-band part for the value — two digits and a multiplier — and disregard the tolerance figure this returns.
- Do surface-mount resistors use color codes?
- No. SMD parts carry printed numeric codes instead: three digits where the last is the number of zeros, so 103 is 10 × 10³ = 10 kΩ, or the EIA-96 scheme where two digits index a value table and a letter gives the multiplier.
- Are the values sent anywhere?
- No. The decode is a lookup table and one multiplication, running in the page. Nothing is uploaded and nothing is stored.
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