Select the color bands to calculate resistance instantly, or flip to reverse mode and enter a resistance value to see the bands you need.
Resistors are too small to print numbers on reliably, so manufacturers use colored bands instead — readable from any angle, even on a component a few millimeters long. Each color stands for a digit, and read together the bands spell out the resistance value in ohms, plus how close to that value the part is guaranteed to be.
Most resistors in hobby kits and general electronics use four bands:
Precision resistors add a third digit band before the multiplier, giving three significant digits instead of two — that's why 5- and 6-band resistors hold tighter tolerances than 4-band ones. When a 6th band is present, it indicates the temperature coefficient: how much the resistance drifts per degree of temperature change, important in precision analog circuits.
| Color | Digit | Multiplier | Tolerance |
|---|
Resistors aren't manufactured at every possible number — they follow standard series like E12 (12 values per decade) so that a manageable set of parts can cover any circuit need. The base E12 values are:
10 · 12 · 15 · 18 · 22 · 27 · 33 · 39 · 47 · 56 · 68 · 82
Multiply any of these by 1, 10, 100, 1k, 10k, and so on to get the full range — 220Ω, 4.7kΩ, and 100kΩ are all E12 values.
Gold and silver almost always appear as the tolerance band, marking ±5% and ±10% respectively. Gold can also serve as a ×0.1 multiplier on some resistors.
Start from the side furthest from the tolerance band. The tolerance band (usually gold or silver, sometimes brown or red on precision parts) is always last and is often spaced slightly apart from the others.
Surface-mount (SMD) resistors use printed numeric codes instead, because they're too small for color bands to be printed or read reliably.
Resistors use colored bands instead of printed numbers because the small cylindrical body doesn't have room for readable text, and colors can be read from any angle. The system has been standardized since the early 20th century and is still universal across manufacturers today.
Most common resistors use either 4 or 5 bands. A 4-band resistor has 2 significant digits, a multiplier, and a tolerance band. A 5-band resistor (used for higher precision) has 3 significant digits, a multiplier, and a tolerance band — giving more precise values. This calculator handles the standard 4-band format most commonly found in general electronics.
Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Grey=8, White=9. The multiplier band uses the same scale as a power of 10 (except Gold=×0.1 and Silver=×0.01 for very low resistances). Many students memorize this with mnemonics like "Bad Boys Race Our Young Girls, But Violet Generally Wins" — one letter per color in order.
A resistor with bands Yellow-Violet-Red-Gold: Yellow=4, Violet=7, so the first two digits are "47." Red multiplier = ×100. So 47 × 100 = 4,700Ω, or 4.7kΩ. Gold tolerance band means ±5% — so the actual resistance could be anywhere from 4,465Ω to 4,935Ω.
If you already know the resistance you need (say, from a circuit design or Ohm's Law calculation) but need to find the physical resistor, use the reverse mode above — enter the value and see which color bands to look for in your parts bin.
Brown = ±1%, Red = ±2%, Gold = ±5%, Silver = ±10%. No tolerance band typically means ±20% (rare on modern resistors). Tighter tolerance resistors cost more but matter for precision applications like audio circuits, sensor references, or timing circuits.
What if my resistor has 6 bands? A 6th band typically indicates a temperature coefficient (how much resistance changes with temperature), common on precision resistors. The first 5 bands still follow the standard 5-band reading.
Why do some resistors have no visible color bands? Surface-mount (SMD) resistors use a printed numeric code instead of color bands due to their small size — a 3-digit or 4-digit code follows similar logic (digits + multiplier) but printed as text rather than colors.
Which end do I start reading from? Start from the band closest to one end of the resistor — the tolerance band (often gold or silver) is usually spaced slightly further from the others and marks the end you read backward from.
Can I verify the color code with a multimeter? Yes — always double-check critical values with a multimeter if precision matters, since color perception can vary and bands can be hard to distinguish under poor lighting.
Does band width matter? No, only the color and position matter — band width is just a manufacturing/visual detail, not part of the encoded value.
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