Resistor Color Code
Choose the band count, then read colors to ohms or encode an exact resistance back to bands.
Decoded resistance
Calculation and copying stay in this browser. Anonymous events contain only decode/encode mode, band-count variant, and the fixed common-commercial profile.
How the resistor color code works
Three- and four-band resistors use two significant digits. Five- and six-band resistors use three. Multiply those digits by the multiplier band's power of ten: brown–black–red is 10 × 10² Ω = 1,000 Ω. A three-band resistor has an implicit ±20% tolerance; the other modes require a tolerance band.
The result keeps the equation, exact value in ohms, normalized engineering notation, and lower and upper tolerance bounds together. Reverse mode only returns a color sequence when the entered decimal is exactly representable by the selected number of significant bands. It never silently chooses a nearby E-series value.
With a nonzero first digit, this profile's theoretical range is 0.1 Ω–99 GΩ for three or four bands and 1 Ω–999 GΩ for five or six bands.
Common commercial resistor color code chart
This interactive profile is common commercial markings (common_commercial_v1). It covers the widely exposed digit, multiplier, tolerance, and 6-band TCR choices below. A dash means that color is not offered for that role.
| Color | Digit | Multiplier | Tolerance | TCR |
|---|---|---|---|---|
| None | — | — | ±20% (implicit 3-band only) | — |
| Silver | — | 10^-2 | ±10% | — |
| Gold | — | 10^-1 | ±5% | — |
| Black | 0 | 10^0 | — | 250 ppm/K |
| Brown | 1 | 10^1 | ±1% | 100 ppm/K |
| Red | 2 | 10^2 | ±2% | 50 ppm/K |
| Orange | 3 | 10^3 | — | 15 ppm/K |
| Yellow | 4 | 10^4 | — | 25 ppm/K |
| Green | 5 | 10^5 | ±0.5% | 20 ppm/K |
| Blue | 6 | 10^6 | ±0.25% | 10 ppm/K |
| Violet | 7 | 10^7 | ±0.1% | 5 ppm/K |
| Gray | 8 | 10^8 | ±0.05% | 1 ppm/K |
| White | 9 | 10^9 | — | — |
Orient the resistor before choosing colors
Begin at the band nearest an end. The gap before the tolerance band is often wider, which can help identify the reading direction. If the spacing is ambiguous, try the reverse reading and compare it with a meter reading and the component datasheet.
Faded paint, lighting, manufacturer-specific markings, non-resistor parts, and six-band reliability variants can make a visual decode wrong. Pink multipliers and uncommon current-IEC precision tolerances are intentionally outside this common-commercial profile; consult the exact part's datasheet rather than forcing an unsupported choice.
Tolerance bounds and TCR estimate
Tolerance bounds use Rmin = R × (1 − tolerance/100) and Rmax = R × (1 + tolerance/100). The calculator represents the significant digits and powers of ten as exact decimal integers, so values such as 0.1 Ω and 49.4 MΩ do not depend on a rounded binary floating-point display.
For a six-band resistor, the optional estimate uses ΔR = R × TCR × 10^-6 × ΔT around 25 °C. Actual limits, temperature range, reference conditions, and nonlinear behavior come from the component datasheet.
Limits and electrical safety
Color bands do not specify power rating, maximum voltage, pulse rating, temperature range, package construction, or whether a circuit is safe. De-energize equipment and isolate the component before measuring resistance. Decoding a plausible value does not make live-circuit work safe.
This page is for axial through-hole resistor markings. It does not decode SMD numeric codes, calculate Ohm's law or resistor networks, size an LED current-limiting resistor, or identify capacitors and inductors.
Frequently asked questions
How do I read a resistor color code?
Start from the band nearest an end. Read two significant digits for a 3- or 4-band resistor, or three for a 5- or 6-band resistor, then apply the multiplier. The next band gives tolerance; a sixth band in this profile gives TCR.
What does a missing tolerance band mean?
A three-band resistor has no separate tolerance band and uses the commercial ±20% convention. Four-, five-, and six-band modes require an explicit tolerance color.
Why can an exact value fail to encode?
The selected band count has only two or three significant digits and this profile admits multipliers from silver 10^-2 through white 10^9. The encoder rejects values that would need rounding, pink, or another unsupported marking.
Does this cover every IEC 60062 color assignment?
No. It uses a clearly labeled common-commercial compatibility profile. IEC 60062 is the normative marking-code family, but uncommon current-edition and manufacturer-specific assignments require the component datasheet.
What does the sixth band show?
In this profile the sixth band shows temperature coefficient in parts per million per kelvin (ppm/K), relative to a reference condition commonly stated around 25 °C. The displayed drift is first-order arithmetic, not a guaranteed resistance at temperature.
Can I measure the resistor in a live circuit?
No. De-energize equipment and isolate the component before measuring resistance. Color bands do not establish whether a circuit is safe to touch or work on.