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:
$$\text{Base} = D_1D_2 \ (\text{or } D_1D_2D_3 \text{ on 5- and 6-band parts})$$
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 $R = 87 \times 10^4 = 870{,}000\ \Omega = 870\ k\Omega$. Tolerance limits follow from the tolerance-band percentage $t$:
$$R_{min} = R(1-t) \qquad R_{max} = R(1+t)$$
Conductance and current draw follow directly from the decoded resistance:
$$G = \frac{1}{R} \qquad I = \frac{V}{R}$$
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)
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×10⁰ | — |
| Brown | 1 | ×10¹ | ±1% |
| Red | 2 | ×10² | ±2% |
| Orange | 3 | ×10³ | — |
| Yellow | 4 | ×10⁴ | — |
| Green | 5 | ×10⁵ | ±0.5% |
| Blue | 6 | ×10⁶ | ±0.25% |
| Violet | 7 | ×10⁷ | ±0.1% |
| Gray | 8 | ×10⁸ | ±0.05% |
| White | 9 | ×10⁹ | — |
| Gold | — | ×10⁻¹ | ±5% |
| Silver | — | ×10⁻² | ±10% |
| No band | — | — | ±20% |
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.