Resistor Color Code Calculator
Decode the colored bands of a 4, 5 or 6 band resistor into ohms, tolerance and range, or type a resistance and get the band colors to look for. The tool also shows the nearest E6, E12, E24 and E96 standard values and runs entirely in your browser.
Bands to value
Value to bands
Nearest standard values
Closest E-series value to the resistance typed in “Value to bands”.
| Series | Typical tolerance | Nearest value | Deviation |
|---|
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How to use the resistor color code calculator
- To read a resistor, choose 4, 5 or 6 bands under “Bands to value”, then pick the color of each band, starting from the end where the bands sit closest to the edge.
- The result gives the resistance, the tolerance, the minimum and maximum value, and for 6 bands the temperature coefficient. The last line says whether the value belongs to a standard E-series.
- To find bands for a known resistance, type it under “Value to bands”: 4700, 4.7k, 4k7, 1M, 2R2, 0.22 and 330 ohm all work. Choose the tolerance and the number of bands.
- If the value needs more digits than the bands can carry, the tool says so, shows the nearest value they can express and offers a button to use it.
- The last card lists the closest E6, E12, E24 and E96 value to your number, with the deviation in percent. Your choices are remembered in this browser.
How to read the color bands
Hold the resistor so the bands are on the left and start from the end nearest to a band. The tolerance band is usually set apart from the others by a larger gap, and on 4 band parts it is almost always gold or silver. Gold and silver never stand for a digit, so a gold or silver band tells you that this end is the last one. The calculator does not offer black for the first band, because a code cannot start with a zero digit.
A 4 band resistor has two digits, a multiplier and a tolerance. A 5 band resistor has three digits, a multiplier and a tolerance, which gives finer steps and is common on precision parts. A 6 band resistor adds a temperature coefficient after the tolerance. The code is also written “resistor colour code” in British English.
How it works
The digit bands form a number and the multiplier band gives a power of ten:
Here d1, d2, d3 are the digit values, x is the multiplier exponent (0 for black up to 9 for white, −1 for gold, −2 for silver), and t is the tolerance in percent. The tool computes with whole numbers scaled by powers of ten, so there is no floating-point noise, and the values shown are exact. Going the other way, it writes your resistance with exactly 2 or 3 digits and a power of ten. If you give more digits than the bands allow, it rounds half up to the digits available.
Resistor color code chart
| Color | Digit | Multiplier | Tolerance | Temp. coeff. |
|---|---|---|---|---|
| Black | 0 | ×1 | – | 250 ppm/K |
| Brown | 1 | ×10 | ±1 % | 100 ppm/K |
| Red | 2 | ×100 | ±2 % | 50 ppm/K |
| Orange | 3 | ×1 k | – | 15 ppm/K |
| Yellow | 4 | ×10 k | – | 25 ppm/K |
| Green | 5 | ×100 k | ±0.5 % | 20 ppm/K |
| Blue | 6 | ×1 M | ±0.25 % | 10 ppm/K |
| Violet | 7 | ×10 M | ±0.1 % | 5 ppm/K |
| Gray | 8 | ×100 M | ±0.05 % | 1 ppm/K |
| White | 9 | ×1 G | – | – |
| Gold | – | ×0.1 | ±5 % | – |
| Silver | – | ×0.01 | ±10 % | – |
The newest edition of the international standard revised a few rarely used tolerance codes, so for precision parts the datasheet decides.
Examples
Example 1: yellow, violet, red, gold. The digits are 4 and 7, the multiplier is ×100, so R = 47 × 100 = 4,700 Ω = 4.7 kΩ. Gold means ±5 %, which is ±235 Ω, so the range is 4.465 kΩ – 4.935 kΩ.
Example 2: brown, black, black, red, brown (5 bands). The digits are 1, 0, 0 and the multiplier is ×100, so R = 100 × 100 = 10,000 Ω = 10 kΩ. Brown means ±1 %, which is ±100 Ω, so the range is 9.9 kΩ – 10.1 kΩ.
Example 3: 2R2 with 4 bands, ±5 %. 2.2 Ω is 22 × 0.1, so the bands are red, red, gold (×0.1), gold (±5 %).
Example 4: 123 Ω. Three digits do not fit 4 bands. The tool offers the nearest value, 120 Ω (brown, red, brown, plus the tolerance band). With 5 bands it fits exactly: brown, red, orange, black.
Tolerance and standard E-series values
Tolerance says how far the real resistance may lie from the marked value. A 4.7 kΩ resistor with ±5 % can measure anything from 4.465 kΩ to 4.935 kΩ.
You cannot buy every value because parts are made in preferred-number series, spaced so that neighboring tolerance ranges just touch. E6 has 6 values per decade (±20 %), E12 has 12 (±10 %), E24 has 24 (±5 %) and E96 has 96 (±1 %). E6, E12 and E24 are lists of rounded two-digit numbers that do not follow the formula exactly: the formula gives 2.61 where the series lists 2.7, and 3.16 where it lists 3.3. E96 follows 10^(i/96), rounded to three digits. For example, 5000 Ω is not a standard value: the nearest is 4.7 kΩ in E12 (−6.0 %), 5.1 kΩ in E24 (+2.0 %) and 4.99 kΩ in E96 (−0.2 %).
Temperature coefficient
The sixth band gives how much the resistance drifts with temperature, in ppm/K (parts per million per kelvin). The change is about R × TC × ΔT / 1,000,000. A 1 kΩ resistor with 100 ppm/K that warms by 50 K changes by 1000 × 100 × 50 / 1,000,000 = 5 Ω. Lower numbers mean a more stable part.
Common reading mistakes
- Reading from the wrong end. Gold, red, violet, yellow is not a valid code, because gold cannot be a first digit. Turn the part around.
- Mixing up red, orange and brown. Poor light, age and dirt make them hard to tell apart. Use daylight on a white background, and confirm with a meter when it matters.
- Choosing the wrong number of bands. Treating a 5 band part as 4 bands shifts the result by a factor of ten or more.
Surface-mount resistors use printed number codes instead of colors, for example 472 for 47 × 10² = 4.7 kΩ or 4R7 for 4.7 Ω. This tool does not decode them.
Frequently asked questions
Which end do I start reading from?
Start at the end where the first band is closest to the edge, with the widest gap before the tolerance band at the other end. A gold or silver band marks the last end.
Why can I not buy a 5000 Ω resistor?
Standard series only contain certain values. Use the nearest one, or combine two resistors in series or parallel.
What does ppm/K mean?
It is the relative change of resistance per kelvin of temperature change, in millionths. 100 ppm/K means 0.01 % per kelvin.
Does this tool read surface-mount codes?
No. It handles the color bands of through-hole resistors only.
Is my data sent anywhere?
No. All calculations run in your browser, nothing is uploaded, and your settings stay in local storage on your device.
Related tools
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- Truth Table Generator – build truth tables for logic circuits.