Resistor Color Code Calculator

How the Resistor Color Code tool works

The resistor color code tool decodes 4-band and 5-band resistor markings into resistance values and tolerance. Select the color of each band from the dropdowns — the result updates instantly to show resistance in ohms, kilohms, or megaohms, plus the tolerance percentage. It also works in reverse: enter a resistance value to find the correct color sequence for marking or ordering resistors.

4-band vs 5-band resistors

Standard through-hole resistors use a 4-band code: two digit bands, one multiplier band, and one tolerance band. Precision resistors (1% tolerance or better) add a third digit band, making 5 bands total. The 4-band format offers tolerance down to 5% (gold band) and 10% (silver band). The 5-band format allows 1% (brown), 0.5% (green), 0.25% (blue), and 0.1% (violet) tolerance resistors common in measurement circuits.

The color code sequence

The standard color-to-digit mapping is: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, grey=8, white=9. The mnemonic "BB Roy of Great Britain had a Very Good Wife" helps memorise this sequence. The multiplier band extends this to cover values from 1 Ω (black multiplier) through 10 MΩ (blue multiplier). Gold and silver multipliers represent ×0.1 and ×0.01 for sub-ohm values.

E-series preferred values

Resistors are manufactured in standardised E-series value sets. E12 (12 values per decade, 10% tolerance) and E24 (24 values, 5%) cover most general-purpose work. E48, E96, and E192 series cover 2%, 1%, and 0.5% precision resistors. The tool displays which E-series the decoded value belongs to, helping you quickly find the nearest standard value when a circuit requires a specific resistance not in your stock.

Reading resistors on real components

The most common identification challenge is distinguishing the first band from the last tolerance band when the resistor orientation is unclear. The tolerance band (gold or silver) is always the last band and is usually separated by a wider gap from the digit bands. Temperature coefficient (PPM) bands appear on some military-grade 6-band resistors as the final band — the tool's 6-band mode handles these as well.

Frequently asked questions

How do I read a 4-band resistor?

A 4-band resistor has four colored stripes: Band 1 is the first significant digit, Band 2 is the second significant digit, Band 3 is the multiplier (power of 10), and Band 4 is the tolerance. For example, Red-Red-Red-Gold reads as 2-2-×100-±5%, which gives 2200 Ω (2.2 kΩ) ±5%. Hold the resistor so the tolerance band (gold or silver) is on the right.

What is the difference between 4-band and 5-band resistors?

A 5-band resistor adds a third significant digit before the multiplier band, enabling more precise resistance values. For example, Brown-Black-Black-Red-Brown = 1-0-0-×100-±1% = 10,000 Ω (10 kΩ) ±1%. Five-band resistors are common in precision applications such as audio circuits, measurement equipment, and tight-tolerance designs requiring 1% or better accuracy.

What does the tolerance band mean?

The tolerance band indicates how much the actual manufactured resistance may deviate from the stated nominal value. Common tolerance colors are: Gold = ±5%, Silver = ±10%, Brown = ±1%, Red = ±2%, Green = ±0.5%, Blue = ±0.25%. For general-purpose circuits, ±5% (gold) is acceptable. For precision analog or measurement circuits, use ±1% or better resistors.