Resistor Color Code Explained: Reading the Four Bands

What the resistor colour code actually encodes

Pick a through-hole resistor out of a parts drawer and look closely at the body. There will be four (sometimes five or six) coloured bands painted around the cylinder, evenly spaced, with the last band slightly further from the rest. Those bands encode the resistor’s value and tolerance in a system specified by IEC 60062 and adopted internationally — the same colours mean the same thing in Tokyo, London, Lagos and San Francisco. The resistor colour code calculator turns the four dropdowns into the resistance in ohms (Ω), kilo-ohms (kΩ) or mega-ohms (MΩ), along with the tolerance min/max range that real parts must fall within.

Four numbers are encoded in four bands: the first significant digit, the second significant digit, the power-of-ten multiplier, and the tolerance band. The arithmetic is the one-liner R = (10·d₁ + d₂) × multiplier in ohms, with a ± tolerance percentage giving the guaranteed range around that nominal. Memorising the colour-to-digit mapping is the only piece that takes time. Everything else — the multiplier exponents, the tolerance meaning, the read direction — falls out from the basic four-band rule.

The full IEC 60062 colour table

The colour code is identical across the world. Bands 1 and 2 are significant digits 0–9. Band 3 is the power-of-ten multiplier. Band 4 is the tolerance. The full mapping:

Digits (bands 1 and 2): black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9. The order matches the visible-light spectrum from infrared (black) through ROYGBV to ultraviolet (white), which is the trick that makes the mapping memorable once you have seen it once. There is no purple — violet does that job. Gray is the boundary colour between violet and white, and there is no “8th colour of the rainbow” to remember separately.

Multiplier (band 3): the same digit colours plus two extras for fractional multipliers. Black ×1 (10⁰), brown ×10, red ×100, orange ×1 000, yellow ×10 000, green ×100 000, blue ×1 M, violet ×10 M, gray ×100 M, white ×1 G. Plus gold ×0.1 and silver ×0.01 for sub-ohm parts. The digit-colour-as-multiplier rule means the same colour can appear in two bands of the same resistor with different meanings (e.g. brown-black-black: digits 1 and 0, multiplier ×1 → 10 Ω).

Tolerance (band 4): brown ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1%, gray ±0.05%, gold ±5%, silver ±10%, no band ±20%. Gold and silver are by far the most common in consumer-grade parts because they are visually distinctive — gold and silver paint never appears in bands 1 or 2, so spotting it at one end of the resistor immediately identifies the read direction.

Worked examples: 10 Ω, 1 kΩ, 47 kΩ, 10 MΩ

Take the most common reference value first — a 10 Ω resistor, the kind used as a series snubber, a current-sense element, or a base-emitter ballast on a power transistor. The colour code is brown-black-black-gold:

Band 1 = brown    → digit 1
Band 2 = black    → digit 0
Band 3 = black    → ×1
Band 4 = gold     → ±5%

R = (10·1 + 0) × 1 = 10 Ω ±5%
Min/max range: 9.5 Ω to 10.5 Ω

The black-as-multiplier ×1 catches a lot of beginners because black is also the digit zero in the second band. There is no way to tell black-zero from black-multiplier except by position; the rule is band 1 and band 2 are always digits, band 3 is always the multiplier, no matter what colour appears. Plug the same colours into the resistor colour code calculator and you get the same 10 Ω read-out with the 9.5–10.5 Ω range and the ±5% tolerance pre-applied.

Scale up by a factor of 100 and you arrive at a 1 kΩ resistor — the most-stocked single value on Earth. Brown-black-red-gold:

Band 1 = brown    → digit 1
Band 2 = black    → digit 0
Band 3 = red      → ×100
Band 4 = gold     → ±5%

R = (10·1 + 0) × 100 = 1 000 Ω = 1 kΩ ±5%
Min/max range: 950 Ω to 1 050 Ω

Now the textbook 47 kΩ pull-up — yellow-violet-orange-gold, the colour combination every electrical engineer learns to recognise on sight:

Band 1 = yellow   → digit 4
Band 2 = violet   → digit 7
Band 3 = orange   → ×1 000
Band 4 = gold     → ±5%

R = (10·4 + 7) × 1 000 = 47 000 Ω = 47 kΩ ±5%
Min/max range: 44.65 kΩ to 49.35 kΩ

And finally a 10 MΩ scope-probe-style high-impedance resistor — brown-black-blue-gold:

Band 1 = brown    → digit 1
Band 2 = black    → digit 0
Band 3 = blue     → ×1 M
Band 4 = gold     → ±5%

R = (10·1 + 0) × 1 000 000 = 10 000 000 Ω = 10 MΩ ±5%
Min/max range: 9.5 MΩ to 10.5 MΩ

Notice that the four examples span six orders of magnitude (10 Ω to 10 MΩ) and only the third band changed — everything else is just colour permutations of the same digit-digit pair. The resistor colour code calculator covers the full decade range from milli-ohms (silver multiplier) through giga-ohms (white multiplier), but in practice 99% of resistors you will meet sit in the 1 Ω to 10 MΩ band.

Why the spectrum order is the only mnemonic that lasts

Generations of electronics students have memorised colourful mnemonics for the digit mapping — every introductory textbook lists at least one, and many are bawdy enough that they would not survive a modern editorial review. The classic “Bad Boys Race Our Young Girls But Violet Generally Wins” maps to Black Brown Red Orange Yellow Green Blue Violet Gray White — 0 through 9.

The mnemonic is fine for cramming the night before a lab exam. For long-term retention the only thing that survives is the underlying logic: digits 1–7 are the visible-light spectrum in physicist’s order (red, orange, yellow, green, blue, indigo-as-violet), digit 8 is the dim version of white (gray), and digit 9 is white itself. Black sits below the spectrum at zero (no light). Once that is the picture in your head you can derive any colour-to-digit mapping cold from first principles, which is faster than running through a memorised string.

Common mistakes when reading resistors

Reading the resistor backwards

By far the most common error. The fix is the gold-or-silver test: gold and silver only appear on the multiplier (×0.1, ×0.01) or the tolerance (±5%, ±10%), never as digit bands. If you read “gold” as your first band you have flipped the resistor and need to read the other way. Yellow-violet-orange-gold read backwards becomes gold-orange-violet-yellow, which is not a valid colour code at all and will jump out as soon as you try to enter it into the resistor colour code calculator.

Confusing brown, red and orange in low light

Tungsten bench lamps make brown look red and red look orange. Magnify or move to daylight, or — most reliably — measure with a multimeter. A 4.7 kΩ (yellow-violet-red-gold) being misread as 47 Ω (yellow-violet-black-gold) is a hundred-fold error that will kill an LED or burn out a transistor base resistor. Older eyes find blue and violet hard to separate too; if in doubt, measure.

Forgetting the multiplier when the value looks small

Brown-black-brown-gold reads 10 × 10 = 100 Ω ±5%, not 10 Ω ±5%. The brown multiplier in band 3 is easy to miss because it looks similar to the brown digit in band 1 if you are scanning quickly. Always read all four bands deliberately; never abbreviate to “oh, another brown-black” before checking band 3.

Treating the rated values as exact

A 47 kΩ ±5% resistor can legitimately measure 44.65 kΩ or 49.35 kΩ. If your circuit needs better than that, you need a tighter tolerance (look for brown tolerance band = ±1%) or a trimmer pot. Never derate a circuit by assuming all your ±5% parts will happen to come in at exactly nominal — they will not.

The E-series: why 47, 22 and 10 keep appearing

Look down a row of resistors in a hobbyist kit and you see 10, 22, 47, 100, 220, 470, 1 k, 2.2 k, 4.7 k, 10 k, 22 k, 47 k and so on — the same six digits multiplied by powers of ten. Those values are not arbitrary; they sit at the grid points of the E-series of preferred values defined by IEC 60063.

The E-series are geometric, with N values per decade spaced by a factor of 10^(1/N). E6 (used for ±20% parts) has six values per decade: 10, 15, 22, 33, 47, 68 — each roughly 1.47× the previous. E12 (±10%) has twelve: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 — each roughly 1.21×. E24 (±5%) has twenty-four. E48, E96 and E192 (for ±2%, ±1% and ±0.5% respectively) keep doubling.

The spacing is chosen so that the tolerance bands of adjacent values just touch. A 47 kΩ ±5% part is allowed up to 49.35 kΩ; the next E24 value, 51 kΩ ±5%, is allowed down to 48.45 kΩ. The two bands overlap slightly so that no matter what value you need within the decade, there is a preferred value whose tolerance range covers it. This is also why some non-E-series values (like 50 kΩ) are not stocked — they would fall in the overlap and would not extend coverage. To hit a non-preferred value you series/parallel two preferred parts, which the resistor colour code calculator does not do directly but is a good companion workflow.

5-band and 6-band resistors

Precision resistors with ±1% or ±2% tolerance need three significant digits, not two, so they use five bands: digit, digit, digit, multiplier, tolerance. A 5-band yellow-violet-black-red-brown reads 470 × 100 = 47 kΩ ±1%, very different from the 4-band yellow-violet-black-red read which would be a (nonsensical) digit-digit-digit-multiplier pattern. The way to tell 4-band from 5-band on sight is the count itself — bands are usually evenly spaced enough that you can count to four versus five in a glance — and the tolerance colour: 5-band parts typically have a brown ±1% or red ±2% tolerance band, where 4-band parts are almost always gold or silver.

6-band resistors add a temperature-coefficient band on the end, in parts-per-million per kelvin. Brown is 100 ppm/K, red 50 ppm/K, orange 15 ppm/K, yellow 25 ppm/K. The temperature coefficient becomes important in voltage references, oven-controlled oscillators and high-precision instrumentation where the resistor’s drift with ambient temperature is a measurable error. For most hobby and general-engineering work you will not meet 6-band parts.

Surface-mount resistors abandon the colour code entirely. Standard chip resistors use a 3-digit code (the first two digits are significant, the third is the power-of-ten exponent, so “472” = 47 × 10² = 4.7 kΩ), a 4-digit code for precision parts (“4702” = 470 × 10² = 47 kΩ), or the EIA-96 system for sub-millimetre packages (a two-digit code that indexes a 96-value table plus a letter that gives the multiplier). The maths is the same; only the encoding changes.

When the calculator isn’t enough

The colour code gives the nominal resistance and tolerance, which is all you need for the vast majority of circuit design and bench work. The cases where you need more:

• Critical drift applications. If your circuit lives over a 100 °C ambient swing and you need better than 0.1% absolute accuracy, look up the temperature coefficient on the part datasheet (or read the 6th band on a 6-band part). The colour code does not encode TCR on 4-band or 5-band resistors.
• High-frequency behaviour. All real resistors have some series inductance (from the body geometry and the leads) and some parallel capacitance, so the effective impedance at high frequencies is not just R. Wirewound parts are particularly inductive; carbon composition was historically used for RF specifically because of low parasitic inductance. The datasheet gives the impedance versus frequency curve; the colour code does not.
• Power and pulse rating. The colour code says nothing about the dissipation rating of the part — that is determined by the physical size and the construction. A 1 W 47 kΩ and a 1/8 W 47 kΩ have the same colour code but very different ratings. Always check the package size against the expected I²R power before sizing.
• Surface-mount parts. These do not have colour codes at all; see the SMD code section above.

Where you will use the colour code in practice

• Bench debugging. Identify the resistor without unsoldering and measuring, when you only need a quick sanity check that the circuit matches the schematic.
• Parts-bin sorting. Recover the value of a loose resistor that has rattled out of its label and back into the general drawer of doom.
• Vintage and repair work. Older boards rarely have silkscreen reference designators tied to part values — the colour code is the only on-board record of what should be there.
• BoM verification. Cross-check a manufactured board against the bill of materials by reading the colour codes of populated resistors and confirming they match the design.
• Education. Teaching beginners to identify components by sight before handing them a multimeter — the colour code is a long-form lesson in encoding systems, standards bodies, and tolerance.

Frequently asked questions

The detailed answers to common questions — which end is band 1, what gold and silver mean, why some values are stocked and others not, how to read 5-band and 6-band parts, what a ±5% tolerance actually guarantees in practice — are listed in the FAQ section on this page. To decode an actual resistor by picking the four band colours and reading off the resistance with its tolerance range, jump back to the resistor colour code calculator. For related electronics tools see the capacitor energy calculator for E = ½ C V², the wavelength calculator for v = f·λ, and the force calculator for Newton’s second law — sister three-variable physics identities that share the same rearrangeable structure as Ohm’s law.