How resistor color codes work
Resistor color bands encode a resistance value using significant digits, a multiplier and a tolerance. The bands are read in order from the end where the significant-digit bands begin.
In a 4-band resistor, two bands provide significant digits. A 5-band resistor uses three significant-digit bands, allowing an additional digit of precision.
4-band resistor formula
For example, brown-black-red gives the digits 1 and 0 with a multiplier of 100. The resistance is therefore 10 × 100 = 1,000 ohms, or 1 kΩ.
5-band resistor formula
A 5-band code such as brown-black-black-brown represents the digits 1-0-0 multiplied by 10, which is also 1,000 ohms.
Digit colors
The digit sequence is black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8 and white 9. The first significant-digit band cannot represent a leading zero in this calculator.
Multiplier bands
After the significant digits, the multiplier scales the value. Black means ×1, brown ×10, red ×100 and the sequence continues by powers of ten. Gold represents ×0.1 and silver represents ×0.01.
Resistor tolerance
The tolerance band describes how far the actual resistance may vary from its nominal value. For example, a 1 kΩ resistor with a ±5% tolerance has a nominal range from 950 Ω to 1.05 kΩ.
Common tolerance colors include brown ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1%, gray ±0.05%, gold ±5% and silver ±10%. A resistor with no tolerance band is represented here as ±20%.
Convert resistance to color bands
The reverse mode converts a resistance value into a 4-band or 5-band color code. Select the desired band count and tolerance, then enter the resistance in ohms, kilohms, megohms or gigohms.
Not every arbitrary decimal value can be represented exactly with a fixed number of significant digits and the available multiplier bands. When an exact representation is not possible, the calculator shows the nearest color-code value and labels it accordingly.
Color appearance can vary with lighting, age and manufacturer. When identification is uncertain, verify the resistor with its documentation or an appropriate measuring instrument before using it in a circuit.
Resistor color code and Ohm's law
A color code tells you the nominal resistance of the component. To use that resistance in circuit calculations, open the Ohm's Law Calculator to calculate voltage, current, resistance or electrical power.
Frequently asked questions
What is the difference between 4-band and 5-band resistors?
A 4-band code has two significant digits, while a 5-band code has three. Both then use a multiplier and tolerance band.
What does a gold multiplier mean?
Gold as a multiplier means ×0.1. Silver as a multiplier means ×0.01.
What does a gold tolerance band mean?
A gold tolerance band means the resistor has a nominal tolerance of ±5%.
Can the calculator generate resistor colors from ohms?
Yes. Switch to Resistance to Colors, enter a resistance value and select either a 4-band or 5-band result.
Why does the reverse calculator sometimes show a nearby value?
A fixed color code has a limited number of significant digits and multipliers. If the entered value cannot be represented exactly, the nearest encodable resistance is shown.
Using this calculator effectively
The Resistor Color Code Calculator decodes 4-band and 5-band resistor colors into resistance and tolerance, and can also convert a resistance value into suggested color bands.
Common uses
- Reading the nominal resistance and tolerance from a 4-band or 5-band resistor.
- Generating a suggested resistor color code from a known resistance value.
- Checking the nominal minimum and maximum resistance implied by a tolerance band.
Tips for a better estimate
- Read the significant-digit bands from the correct end of the resistor before entering the colors.
- Distinguish multiplier colors from tolerance colors because gold and silver have different meanings depending on band position.
- Verify uncertain physical colors with documentation or measurement because lighting, age and manufacturer appearance can make bands difficult to identify.
Related calculations
Ohm's Law Calculator · Amps to Watts Calculator · Voltage Drop Calculator