How to use it
- Choose Colours → value, pick 4, 5 or 6 bands and set each band from its list (or click the bands on the drawing to step through the colours). The resistance, tolerance range and temperature coefficient update immediately.
- Choose Value → colours and type a resistance (4700, 4.7k, 4k7, 2M2). Select the E-series your parts come from; the tool snaps to the nearest standard value and draws its bands.
- Choose SMD code for chip resistors: type the printed marking (472, 4702, 4R7 or an EIA-96 code such as 01A) to get the value.
- Copy the result or the link; the band colours travel in the link so you can share a particular resistor.
Example
A resistor with the bands yellow, violet, red, gold: yellow = 4 and violet = 7 give the digits 47; red as the third band is ×100, so 47 × 100 = 4,700 Ω = 4.7 kΩ; gold is ±5%, so the real part measures between 4,465 Ω and 4,935 Ω. The same value as a 5-band ±1% part is yellow, violet, black, brown, brown (470 × 10). Going the other way, 4.8 kΩ typed into “Value → colours” with E24 selected gives 4.7 kΩ (−2.1%), because 4.8 is not an E24 number; with E96 it gives 4.75 kΩ, drawn as yellow–violet–green–brown–brown.
How the colour code works
Hold the resistor so the bands sit nearer the left end (the tolerance band is spaced a little apart, and on ±5% parts it is the gold one). Read the significant digits first, multiply by the multiplier band, then apply the tolerance.
4-band: R = (d1 d2) × multiplier ± tolerance
5-band: R = (d1 d2 d3) × multiplier ± tolerance
6-band: R = (d1 d2 d3) × multiplier ± tolerance, tempco in ppm/K
yellow violet red gold → 47 × 100 = 4,700 Ω ±5%
range = 4,700 × (1 ∓ 0.05) = 4,465 Ω … 4,935 ΩThe colour assignments follow IEC 60062:2016, which also defines the tolerance letters (F = ±1%, G = ±2%, J = ±5%, K = ±10%, M = ±20%) and the temperature-coefficient letters used in part numbers. The rarer tolerance colours (orange ±0.05%, yellow ±0.02%, grey ±0.01%) and tempco colours (black 250, brown 100, red 50, orange 15, yellow 25, green 20, blue 10, violet 5, grey 1 ppm/K) come from the same standard. Grey was ±0.05% in older charts; the current edition lists it as ±0.01%.
E-series preferred values (IEC 60063)
Each series divides a decade into equal ratio steps (the n-th root of 10), so a ±10% part from E12 overlaps its neighbours just enough to cover every value. The tool rounds in the same ratio sense, which is why 9.9 Ω snaps up to 10 Ω.
| Series | Tolerance | Values per decade |
|---|---|---|
| E6 | ±20% | 1, 1.5, 2.2, 3.3, 4.7, 6.8 |
| E12 | ±10% | 1, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 |
| E24 | ±5% | 1, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.7, 3, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1 |
| E96 | ±1% | 1.00, 1.02, 1.05 … 9.76 (96 values, three significant digits) |
SMD markings
Three-digit codes are two digits plus a power of ten (472 = 47 × 10² = 4.7 kΩ), four-digit codes three digits plus the power (4702 = 47 kΩ), and the letter R, K or M stands in for the decimal point (4R7 = 4.7 Ω, 2K2 = 2.2 kΩ). EIA-96 codes for ±1% parts use two digits for the position in the E96 list and a letter for the multiplier: Z ×0.001, Y or R ×0.01, X or S ×0.1, A ×1, B or H ×10, C ×100, D ×1 k, E ×10 k, F ×100 k – so 01A is 100 Ω and 68C is 49.9 kΩ. A marking of 0 or 000 is a zero-ohm link.
Sources: IEC 60062:2016 – Marking codes for resistors and capacitors, IEC 60063 – Preferred number series for resistors and capacitors, Wikipedia – Electronic color code, Wikipedia – E series of preferred numbers.
Reading tips and limits
Red, orange and brown are easy to confuse under warm light, and old parts fade – when in doubt, measure with a multimeter. A 5-band resistor whose fifth band is a reliability or military band (an older convention) will read wrongly here; this tool follows the IEC meaning where the fifth band is the tolerance. Pink (×0.001) and the single-band zero-ohm link are not offered as colour choices; a zero-ohm part is handled by typing 0 or the SMD code 000.
Questions
- Which end of the resistor do I start reading from?
- Start from the end where the bands are grouped closer together; the tolerance band sits a bit further from the others and is often gold or silver, which never appear as the first digit. If the bands are evenly spaced, the first band is usually nearer one end of the body.
- What does a 4-band resistor with brown, black, red, gold mean?
- Brown 1 and black 0 give 10, red multiplies by 100: 1,000 Ω = 1 kΩ, and gold means ±5%, so the real value is between 950 Ω and 1,050 Ω.
- Why can I not get 4.75 kΩ on a 4-band resistor?
- A 4-band code holds only two significant digits, so it can express 4.7 kΩ or 4.8 kΩ but not 4.75 kΩ. Three-digit values such as the E96 series need a 5- or 6-band resistor; the tool switches the drawing to 5 bands and says so.
- What is the difference between a 5-band and a 6-band resistor?
- Both have three digit bands, a multiplier and a tolerance. The sixth band gives the temperature coefficient in ppm/K – how much the resistance drifts per kelvin – which matters in precision circuits. Brown (100 ppm/K) and red (50 ppm/K) are the most common.