About Resistor Color Code Calculator — 4, 5 & 6 Band
Every leaded resistor carries its value painted on in the color code of IEC 60062: two or three significant-digit bands, a multiplier band, a tolerance band, and — on precision 6-band parts — a temperature-coefficient band. This calculator reads the code in both directions. Pick the band colors and it returns the resistance, the guaranteed min–max window the tolerance implies, and the tempco in ppm/K; or type a target resistance and it generates the band colors, snapped to the nearest standard value of the E24 (±5%) or E96 (±1%) preferred-number series of IEC 60063.
The tables are exact by standard, not convention: black through white are the digits 0–9, the multiplier runs from silver (×0.01) and gold (×0.1) up to white (×10⁹), and the tolerance colors span silver ±10% down to grey ±0.01% in the 2016 edition of IEC 60062. The snap direction matters too — when your target is not a standard value (say 4.8 kΩ), the tool tells you so, shows the nearest catalog value (4.7 kΩ), and marks the result as approximate rather than silently pretending 4.8 kΩ resistors exist.
How It Works
- Choose the band count first. Four bands = two significant digits (the ±5% E24 world: 47 → 4.7 kΩ with a red ×100 band). Five bands = three digits (the ±1% E96 world: 100 → 1.00 kΩ). Six bands add the temperature coefficient after the tolerance band.
- Reading direction: hold the resistor with the tolerance band (usually gold or silver, slightly separated) on the RIGHT. The digits read left to right, then the multiplier, then tolerance, then tempco. If the code reads to a nonsense value one way (e.g. starting on gold), it is backwards.
- For bands → value: pick each band's color and read the nominal resistance, plus the min–max window — a 4.7 kΩ ±5% part is guaranteed between 4,465 and 4,935 Ω. That window is what the tolerance actually promises; the nominal is just the center.
- For value → bands: enter the resistance and pick the tolerance. ±5% snaps to the E24 series (24 values per decade) and prints a 4-band code with a gold tolerance band; ±1% snaps to E96 (96 values per decade) and prints a 5-band code with a brown band. If your value is not in the series, the tool shows the nearest standard value and flags the substitution.
- On 6-band precision parts, the last band is the temperature coefficient: brown = 100 ppm/K means the resistance moves at most 0.01% per °C — a 1 kΩ part drifts about 1 Ω over a 10 °C swing. Lower tempco colors (blue 10, violet 5, grey 1 ppm/K) mark measurement-grade parts.
Worked Example
A resistor reads yellow, violet, red, gold. Yellow = 4 and violet = 7 give the significand 47; red is the ×100 multiplier, so the value is 47 × 100 = 4,700 Ω = 4.7 kΩ; gold is ±5%, so the part is guaranteed between 4,700 × 0.95 = 4,465 Ω and 4,700 × 1.05 = 4,935 Ω. Running the other direction: asking the tool for 4,800 Ω at ±5% cannot return an exact code, because 4.8 is not one of the 24 E24 mantissas — the neighbors are 4.7 (2.1% away) and 5.1 (6.3% away), so it snaps to 4.7 kΩ, prints yellow-violet-red-gold, and flags that the printed code is the nearest standard value, not your exact number.
Formulas
- Decoded value (4-band)
R = (10·d₁ + d₂) × m- Decoded value (5/6-band)
R = (100·d₁ + 10·d₂ + d₃) × m- Tolerance window
R_min = R·(1 − t/100); R_max = R·(1 + t/100)- Temperature coefficient (6th band)
ΔR/R = TC × ΔT × 10⁻⁶
Standards & References
- IEC 60062:2016 — Marking codes for resistors and capacitors: digit, multiplier, tolerance, and temperature-coefficient color assignments (Table 1). Note the 2016 tolerance additions: orange ±0.05%, yellow ±0.02%, grey ±0.01% — older EIA-style charts often print grey as ±0.05%
- IEC 60063 — Preferred number series: E24 (±5%, 24 values/decade) and E96 (±1%, 96 values/decade) used for the value → bands snap; series values verified against Vishay doc 28372
Frequently Asked Questions
How do I tell which end of the resistor to start reading from?
Start opposite the tolerance band: gold or silver can never be a first digit (they are only multipliers or tolerances), and the tolerance band usually sits with a slightly wider gap from its neighbors. On 5- and 6-band precision parts where all bands are colors that could be digits, use the gap, and sanity-check both readings — one direction usually produces a non-standard value, and this calculator's reverse mode will tell you whether a candidate reading is actually in the E24 or E96 series.
What is the difference between 4-band and 5-band codes?
Resolution. Four bands carry two significant digits — enough to name every E24 (±5%) value like 4.7 kΩ. Five bands carry three digits, needed because the E96 (±1%) series has values like 4.99 kΩ and 10.2 kΩ that two digits cannot express. The tolerance band matches: 4-band parts are usually gold (±5%), 5-band parts brown (±1%). The sixth band, when present, adds the temperature coefficient and changes nothing about the value.
The calculator says my value is not standard — can I still buy it?
Not off the shelf in that series. Resistors are manufactured only at the preferred-number points of IEC 60063 — asking for 4.8 kΩ at ±5% gets you the neighbors 4.7 or 5.1 kΩ. The tool snaps to the nearest and flags it. If you genuinely need a non-series value, move to a tighter series (E96's 4.87 kΩ is 1.5% from 4.8 kΩ), combine two resistors in series or parallel, or use a trimmer.
What does the 6th band actually mean in practice?
It bounds thermal drift. Brown (100 ppm/K) means at most 0.01% resistance change per degree: a 10 kΩ part moves up to 10 Ω across a 10 °C room-temperature swing — irrelevant for an LED resistor, fatal in a precision voltage divider. Red (50), blue (10), and violet (5 ppm/K) mark progressively better film; grey (1 ppm/K) is metrology territory. If your circuit has a gain or threshold set by a resistor ratio, match tempcos, not just tolerances.
Is grey ±0.05% or ±0.01%? Charts disagree.
Per IEC 60062:2016 Table 1, grey is ±0.01%; orange is ±0.05% and yellow is ±0.02% — both tolerance assignments were added in the 2016 edition. Many freely-circulating charts predate that edition or copy one that did, and print grey as ±0.05%. This calculator follows the current standard. In practice the ambiguity rarely bites: sub-0.1% parts are usually marked with printed digits (like the IEC 60062 letter-and-number code), not paint bands.
Do gold and silver ever appear as digit bands?
Never as significant digits — gold and silver are only multipliers (×0.1 and ×0.01) or tolerances (±5% and ±10%). That asymmetry is deliberate: it is what makes the reading direction decidable. A gold band as the multiplier is how sub-10 Ω values get coded: 4.7 Ω is yellow-violet-gold(×0.1)-gold(±5%), and 0.47 Ω uses silver (×0.01). The calculator rejects gold or silver in a digit position rather than guessing.