How This Calculator Works
Pick a band count above, then click the color that matches each stripe on your physical resistor — the SVG resistor and the result panel redraw the instant you change a color, with no calculate button to press. Behind the scenes, each color you select maps to a digit, a multiplier, or a percentage using the same IEC 60062 color code standard printed in the reference chart further down this page, and the calculator runs the appropriate formula for whichever band count is active (two significant digits for 3 and 4-band parts, three for 5 and 6-band parts). Switch to the Reverse Lookup tab to work in the opposite direction: type in a target resistance and desired tolerance, and the calculator works out which colors to look for, rounding to the nearest valid significant-figure combination for the band count you choose.
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Anatomy of a 4-Band Resistor
A standard four-band resistor is the configuration most people encounter in general electronics, and it packs three pieces of information into four painted stripes. The first two bands are significant figures — read together as a two-digit number using the color-to-digit chart below, where black is 0 and white is 9. The third band is the multiplier, which tells you how many powers of ten to scale that two-digit number by; in the example below, a red third band multiplies by 100. The fourth and final band is tolerance, printed as a percentage that states how far the actual resistance is allowed to deviate from the nominal value on the label — gold means ±5%, silver means ±10%, and if there's no fourth band at all, the part is assumed to carry a loose ±20% tolerance.
Reading the example above: orange (3) and orange (3) give the digits "33," the red multiplier band scales that to 3,300, and the gold tolerance band means the true resistance sits anywhere from 3,135Ω to 3,465Ω. That's exactly what the 4-Band tab of the calculator above will show you if you select those same four colors.
5-Band and 6-Band Resistors: Extra Precision
Coded components have at least three bands: two significant-figure bands and a multiplier. But other variations are common, particularly on components built to tighter specifications. Adding a third significant-figure band — making five bands total — lets the resistor encode a more precise value before it gets rounded by the multiplier, which is why precision resistors rated at ±1% or ±2% almost always use five bands rather than four. This shifts the multiplier and tolerance bands one position to the right compared to a standard four-band part, into the 4th and 5th positions instead of the 3rd and 4th.
On the most precise resistors, a sixth band appears after the tolerance band: the temperature coefficient, measured in parts per million per degree Celsius (ppm/K). This describes how much the resistance drifts as the component heats up or cools down during operation — a real concern in precision analog circuits, calibration equipment, and measurement instruments, where a resistor that shifts value with temperature can throw off an entire circuit's accuracy. General-purpose electronics work can safely ignore this band, since standard 4 and 5-band resistors are typically stable enough for non-critical applications.
Reading the example above: three significant-figure bands give "330," the brown multiplier scales that by 10 to reach 3,300Ω again, the second brown band tightens the tolerance to ±1% (a range of just 3,267Ω to 3,333Ω), and the blue temperature coefficient band specifies a drift of 10 ppm/K — meaning the resistance shifts by only 0.001% per degree Celsius of temperature change, tight enough for precision instrumentation.
Complete Resistor Color Code Chart
| Color | 1st / 2nd / 3rd Digit | Multiplier | Tolerance | Temp. Coefficient |
|---|---|---|---|---|
| Black | 0 | ×1 | — | 250 ppm/K |
| Brown | 1 | ×10 | ±1% | 100 ppm/K |
| Red | 2 | ×100 | ±2% | 50 ppm/K |
| Orange | 3 | ×1,000 | — | 15 ppm/K |
| Yellow | 4 | ×10,000 | — | 25 ppm/K |
| Green | 5 | ×100,000 | ±0.5% | 20 ppm/K |
| Blue | 6 | ×1,000,000 | ±0.25% | 10 ppm/K |
| Violet | 7 | ×10,000,000 | ±0.1% | 5 ppm/K |
| Grey | 8 | ×100,000,000 | ±0.05% | — |
| White | 9 | ×1,000,000,000 | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
| No band | — | — | ±20% | — |
The Math Behind Each Band Count
All resistor color code math follows the same basic shape — read the significant digits as one number, then scale it by the multiplier — but the number of significant digits changes with the band count.
4-band: Resistance = (10 × Digit1 + Digit2) × Multiplier
5-band and 6-band: Resistance = (100 × Digit1 + 10 × Digit2 + Digit3) × Multiplier
For example, a resistor with bands Orange-Orange-Red-Gold reads as digits 3 and 3, multiplied by ×100 (red), giving 3,300Ω or 3.3kΩ, with a gold tolerance band meaning the actual value falls anywhere between 3.135kΩ and 3.465kΩ. Add a third digit for a 5-band part — say Orange-Orange-Black-Brown-Brown — and you get digits 3, 3, 0 multiplied by ×10 (brown), landing on 3,300Ω again but now specified to a tighter ±1%.
3-Band, 4-Band, 5-Band, and 6-Band: What Changes
- 3-band — two significant digits and a multiplier, no tolerance band at all. Treated as a wide ±20% tolerance by convention. Uncommon on modern parts but still shows up on older or ultra-low-cost components.
- 4-band — the most common configuration on general-purpose resistors: two digits, a multiplier, and a tolerance band, typically gold (±5%) or brown (±1%).
- 5-band — adds a third significant digit for finer resolution, standard on precision resistors rated ±1% or ±2%.
- 6-band — everything in a 5-band resistor plus a temperature coefficient band, used where resistance needs to stay stable across a temperature range, such as in measurement instruments or high-precision analog circuits.
Reverse Lookup: From Ohms to Colors
Going the other direction is just as common — you know you need a 4.7kΩ resistor for a design and want to confirm which bands to look for in a parts bin. The reverse lookup tab above takes your target resistance, unit, desired tolerance, and band count, then works out the matching digit and multiplier colors automatically. This is especially useful when sorting through mixed resistor kits where the printed labels have worn off or the parts were never labeled to begin with.
Resistors in Series & Parallel
Resistors are circuit elements that impart electrical resistance, and real circuits rarely use just one in isolation. How several resistors combine into a single effective resistance depends entirely on whether they're wired in series or in parallel — the two are opposites, and mixing them up is one of the most common mistakes in circuit analysis.
Resistors in series
When resistors are connected end-to-end along a single path, the same current has to flow through every one of them in turn, and the total resistance is simply the sum of each individual resistance:
Rtotal = R1 + R2 + R3 + … + Rn
Adding a resistor in series always increases total resistance, since current now has one more obstacle to push through. The Resistors in Series tool above this article does this addition instantly for any list of values you enter.
Resistors in parallel
When resistors are wired side-by-side across the same two nodes, each one offers current a separate path, and the full voltage is applied across every branch simultaneously. Total resistance is the reciprocal of the sum of reciprocals:
1 / Rtotal = 1/R1 + 1/R2 + 1/R3 + … + 1/Rn
Adding a resistor in parallel always decreases total resistance below the smallest individual resistor in the group, since current gains an additional path to flow through. The Resistors in Parallel tool above runs this reciprocal-sum calculation automatically — just enter your values separated by commas.
Resistance of a Conductor
Beyond discrete resistors, any length of wire has some resistance of its own, which becomes significant over long cable runs or with thin gauges. The Resistance of a Conductor tool above calculates this directly from a wire's physical dimensions and material using the standard formula:
R = ρ × L / A
Here ρ (rho) is the material's electrical resistivity in ohm-meters, L is the wire's length, and A is its cross-sectional area, calculated from the diameter you enter. Copper and silver have very low resistivity and dominate general wiring; nichrome, at the opposite extreme, has high resistivity on purpose and is the standard choice for resistive heating elements. This tool is useful for estimating voltage drop over a long run of speaker cable, extension cord, or hookup wire before you commit to a gauge.
Frequently Asked Questions
How do I know which side to start reading a resistor from?
Start from the side where the bands are grouped closer together, leaving a wider gap before the last band. That last, more-isolated band is almost always the tolerance band (commonly gold or silver), so reading toward it confirms you're going the correct direction. If the tolerance color is ambiguous, the multiplier band is also a clue since black, gold, and silver multipliers are rare as a first band.
What is the difference between a 4-band and a 5-band resistor?
A 4-band resistor encodes two significant digits, a multiplier, and a tolerance, which is precise enough for general-purpose resistors around 5-20% tolerance. A 5-band resistor adds a third significant digit before the multiplier, allowing tighter tolerances like 1% or 2% since the extra digit reduces rounding error. Most precision resistors use 5 or 6 bands for this reason.
What does the gold or silver band mean on a resistor?
On a 4-band or 5-band resistor, gold or silver in the final position is the tolerance band: gold means the actual resistance is within plus-or-minus 5% of the printed value, and silver means plus-or-minus 10%. Gold and silver are reserved for tolerance or multiplier roles and never appear as a significant-digit band, which is part of why they help you identify the reading direction.
What is the 6th band on a resistor used for?
The sixth band specifies the temperature coefficient, measured in parts per million per degree Celsius (ppm/K). It tells you how much the resistance drifts as the resistor heats up or cools down, which matters in precision analog circuits, measurement equipment, and anywhere stable resistance over a temperature range is critical. Everyday electronics projects can usually ignore this band.
Why do two resistors with the same color bands sometimes measure slightly different resistance?
That's exactly what the tolerance band accounts for — manufacturing isn't perfect, so a resistor marked as 1kΩ with a 5% gold tolerance band could genuinely measure anywhere from 950Ω to 1,050Ω and still be within spec. For circuits sensitive to exact resistance, use a multimeter to measure the actual value rather than relying on the color-coded nominal figure alone.
Why does adding resistors in parallel lower the total resistance?
Because each additional resistor opens up another path for current to flow through, and more available paths means less overall opposition to current — the same reason opening a second checkout lane at a store reduces the total wait, even though each individual lane didn't get any faster.
This calculator is provided for educational and reference purposes. While the color code standard used here matches industry conventions (IEC 60062), always verify critical circuit components with a multimeter before soldering.