Ohms to Resistor Color Code

This is the decoder run backwards: you enter the resistance and the page returns the colour of every band, the multiplier and tolerance included, with a drawing of the component beside it. The input accepts both the plain number and the engineering notation used on schematics — 4700, 4k7, 4.7k, 2M2 and 0R47 are all read the same way, which removes a whole class of extra-zero typos. For 4700 Ω in four bands at 5% tolerance the answer is yellow, violet, red and gold. Switch to five bands and the same value becomes yellow, violet, black, brown and gold, because the third digit joins the calculation.

Internally the value is decomposed into a two or three digit integer times a power of ten, and that exponent becomes the multiplier colour — silver for ×0.01, gold for ×0.1, black for ×1 and onwards to white for ×10⁹. That fixes what the code can represent, and the limit shifts with the band count: four bands span 0.1 Ω to 99 GΩ, five bands span 1 Ω to 999 GΩ, because the first digit can never be zero. Outside it the page refuses rather than inventing a colour. Rounding is stated rather than hidden: 4620 Ω in four bands does not fit in two digits and comes out as 4.7 kΩ, with a note that the difference is 1.73%. In five bands that same 4620 is exact, which is precisely why five-band resistors exist.

It is worth remembering what a colour code is not. It carries the nominal value, not the measured one, and the tolerance band is the promise of how far the part may drift — which is why the tolerance selector changes the last band and nothing else. There is no commercial-series filter here either: ask for 4620 Ω in five bands and the page will emit the colours, but what guarantees such a part exists is the E96 series, not this tool. In practice the common use runs the other way round from what it looks like: you calculated a design resistance, rounded it to the nearest stocked value, and now want to know which colours to hunt for in the parts drawer.