Resistor Color Code Calculator

A resistor color code calculator converts colored bands into precise resistance values, tolerance ranges, and multiplier data for verifying parts across electronic circuit designs.

Decode a Resistor's Color Bands Into Ohms, Tolerance and Conductance

This resistor color code calculator turns the painted bands on a through-hole resistor into a numeric resistance value, tolerance range, and derived conductance. Hobbyists, electronics technicians, and design engineers use it to identify a component's value directly from its markings, without reaching for a multimeter.

How to Use the Resistor Color Code Calculator

Choose the number of bands (3 to 6), then pick the color shown for each significant-digit band, the multiplier band, the tolerance band, and - on 6-band parts - the temperature coefficient band. The calculator returns decoded resistance, tolerance range, conductance, and current draw at reference voltages.

Resistor Color Code Formula: From Bands to Ohms

The color-to-value mapping is defined by IEC 60062, Marking Codes for Resistors and Capacitors, the international standard governing this system. Each color represents a digit 0-9 for the significant-figure bands, and the same colors - plus gold and silver - double as multiplier and tolerance codes depending on which band position they occupy.

The significant-digit bands form a base number:

$$\text{Base}=D_1{D}_2(\text{or }{D}_1{D}_2{D}_3\text{ on 5- and 6-band parts})$$

The multiplier band scales that base by a power of ten matching its own digit value:

$$R=\text{Base}\times 10^n$$

For Gray-Violet-Yellow-Violet: $\text{Base}=87$, multiplier $n=4$ (Yellow), so $R=87\times 10^4=870,000\Omega =870k\Omega$. Tolerance limits follow from the tolerance-band percentage $t$:

$$R_{min}=R(1-t)R_{max}=R(1+t)$$

Conductance and current draw follow directly from the decoded resistance:

$$G=\frac{1}{R}I=\frac{V}{R}$$

Common input mistake: reading the bands starting from the wrong end. The significant-digit bands come first; the tolerance band - usually set apart from the others - comes last. Reading in reverse decodes an entirely different digit sequence.

A nuance most calculators don't flag: a genuine 4-band resistor carrying a Violet (±0.1%) tolerance band, as in this example, isn't something you'd typically find on a supplier's shelf.

A 4-band format only encodes two significant digits, and ±0.1%-precision parts need a third significant digit to make that tolerance meaningful - which is why real ±0.1% resistors are manufactured as 5-band or 6-band parts, not 4-band ones.

The color code system itself doesn't forbid the combination, and this calculator will decode it correctly, but it's worth knowing the pairing is a decoding exercise rather than something matching a stocked component.

Resistor Band Diagram: Reading Order for a 4-Band Resistor

Resistor Color Code Table (per IEC 60062)

Common Questions About the Resistor Color Code Calculator

Why does a 4-band resistor show "N/A" for temperature coefficient?

Because temperature coefficient is only marked with an added 6th band. A 4-band resistor's physical markings simply don't carry that information, so "N/A" is the correct decoded result, not a tool limitation.

Which direction do I read the color bands?

Start from the significant-digit bands, usually grouped closer together, and read toward the tolerance band, which sits apart or is noticeably wider. Reading backward decodes a different value entirely.

Why do gold and silver mean different things in different positions?

Position determines meaning. As a multiplier, gold means ×0.1 and silver ×0.01; as a tolerance, gold means ±5% and silver ±10%. The same color carries two different meanings depending on which band it occupies.

Is a ±0.1% tolerance realistic on a 4-band resistor?

Not in typical manufacturing. Two significant digits don't carry enough resolution for ±0.1% accuracy - real parts at that tolerance are made with a third digit, as 5-band or 6-band resistors, not 4-band ones.

Why does the calculator show conductance and current draw for a resistor?

They're derived directly from the decoded resistance using $G=1/R$ and $I=V/R$, so you get the inverse relationship and expected current at common reference voltages without a separate calculation.