Resistor Color Code Calculator

Resistor color code calculator for 4-band, 5-band, and 6-band resistors

Resistors are often marked with colored bands instead of printed numbers, especially on through-hole parts and older components. The bands encode a resistance value (in ohms), a tolerance (how far the real value can vary), and sometimes a temperature coefficient. This resistor color code calculator helps you translate band colors into a readable resistance and range, and it can also generate a reasonable set of band colors if you already know the resistance you need.

If you are troubleshooting a circuit, the most common need is decoding: you see the bands on a resistor and want to know if it is 220 Ω, 2.2 kΩ, 22 kΩ, or something else. This tool supports 4-band, 5-band, and 6-band decoding. It calculates the nominal resistance, shows the tolerance percentage, and gives a minimum and maximum value range so you can quickly judge whether a measured resistance is within spec.

If you are designing or ordering parts, the second common need is encoding: you know the target resistance (for example 4.7 kΩ) and want to confirm what the bands should look like, or you want a close match if your exact value is not available in a given tolerance series. In encode mode, you enter the target resistance and unit, pick a tolerance, then the calculator outputs a standard band set that represents a close, practical resistor value for either 4-band (2 significant digits) or 5-band (3 significant digits).

Assumptions and how to use this calculator

• 4-band resistors use 2 significant digits plus a multiplier, then a tolerance band. 5-band and 6-band resistors use 3 significant digits plus a multiplier, then a tolerance band.
• Decode results assume standard resistor color meanings: digits 0 to 9, multiplier values including gold (0.1) and silver (0.01), and common tolerance colors.
• If you select 6-band, the last band is treated as temperature coefficient in parts per million per degree Celsius (ppm/°C). The calculator reports what that implies for drift per 10°C as a simple reference.
• Encode mode prioritizes practical banding: it uses 2 digits for 4-band and 3 digits for 5-band, then chooses an appropriate multiplier to represent a close value. If your exact value cannot be represented at that digit precision, the output is a closest match, and the result tells you the represented resistance.
• This tool does not identify physical orientation for every resistor style. Many resistors have a slightly wider gap before the tolerance band. If your reading seems off by a factor of 10 or 100, flip the band order and try again.

Common questions

How do I know if my resistor is 4-band or 5-band?

Most general-purpose resistors with a gold or silver tolerance band are 4-band. Precision resistors often use 5 bands and may have a brown tolerance band (1%) or other tighter tolerances. If there are five colored bands with no obvious “spaced” tolerance band, it is likely a 5-band part. When in doubt, select 5-band and see if the value looks realistic for the circuit.

What does the tolerance range mean for real measurements?

Tolerance means the resistor’s actual resistance can vary from its nominal value by the stated percentage at manufacture. For example, a 1 kΩ resistor at 5% tolerance can be anywhere from 950 Ω to 1050 Ω and still be considered in spec. When measuring in-circuit, other components in parallel can also affect the reading, so use the range as a guide, not absolute proof of failure.

What is the multiplier band doing?

The multiplier band scales the significant digits. For instance, digits “47” with a multiplier of 100 becomes 4700 Ω (4.7 kΩ). A gold multiplier represents 0.1 and silver represents 0.01, which are used for low-ohm resistors. If your decoded result seems too large or too small, multiplier interpretation or band orientation is the usual cause.

When does the 6th band (tempco) matter?

Temperature coefficient matters when the resistor value must remain stable across temperature changes, such as in precision analog circuits, sensors, or reference networks. A value like 100 ppm/°C means the resistance changes about 0.01% per °C. This calculator shows an approximate drift per 10°C so you can quickly estimate whether the temperature effect is meaningful in your application.

Why does encode mode sometimes return a “closest match” value?

A 4-band resistor can only represent two significant digits, so not every resistance can be represented exactly. For example, 4730 Ω cannot be expressed precisely with only two digits and a multiplier, so the closest representable values are 4.7 kΩ or 4.8 kΩ depending on rounding. A 5-band resistor has three digits and can represent more values exactly, which is why it is common for tighter tolerances.