# What is my resistor value?

Reads a 4-, 5- or 6-band resistor colour code (IEC 60062): the resistance, the tolerance, the lowest and highest resistance, and the temperature coefficient.

- Page: https://www.acalculator.org/physics/resistor-color-code-calculator
- JSON spec: https://www.acalculator.org/physics/resistor-color-code-calculator.json
- Version: fb534847dfc1

## Default answer

Example with the default inputs (Number of bands 4 bands, First band Yellow (4), Second band Violet (7), Multiplier band Red (×10²), Tolerance band Gold (±5%)): The bands mean 4.7 kΩ ± 5%: from 4.465 kΩ to 4.935 kΩ.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| bands | Number of bands | 4 bands: 2 digits; 5 bands: 3 digits; 6 bands: 3 digits and a temperature coefficient. |
| b1 | First band | The colour of the first band, a significant digit from black (0) to white (9). |
| b2 | Second band | The colour of the second band, a significant digit from black (0) to white (9). |
| b3 | Third band | The colour of the third band, a significant digit from black (0) to white (9). |
| mult | Multiplier band | The colour of the multiplier band: the power of ten the digits are multiplied by. |
| tol | Tolerance band | The colour of the tolerance band; no band means ±20%. |
| tc | Temperature coefficient band | The colour of the sixth band: how much the resistance changes per kelvin, in ppm/K. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| resistance | Resistance | The digits times the multiplier, in Ω, kΩ, MΩ or GΩ. |
| ohms | Resistance in ohms | The resistance in ohms. |
| tolerance | Tolerance | How far the real resistance may be from the marked value, plus or minus. |
| min | Lowest resistance | The resistance × (1 − tolerance). |
| max | Highest resistance | The resistance × (1 + tolerance). |
| tempco | Temperature coefficient | On 6-band resistors: the change in resistance per kelvin, in parts per million. |
| digits | Colour code | The bands as digits and multiplier: digits × 10^power. |

## Method

R = (significant digits) × 10^(multiplier power); lowest = R × (1 − tolerance); highest = R × (1 + tolerance).

## Assumptions

- Read the bands from the end where they start; the tolerance band is usually set apart from the others.
- Colours follow IEC 60062:2016; older resistors may use other tolerance colours.

## Worked examples

1. bands = 4, b1 = yellow, b2 = violet, mult = red, tol = gold gives resistance = 4.7 kΩ, ohms = 4,700, tolerance = 5%, min = 4.465 kΩ, max = 4.935 kΩ. Source: IEC 60062:2016 Marking codes for resistors and capacitors, colour code table as given in “Electronic color code” (https://en.wikipedia.org/wiki/Electronic_color_code, retrieved 2026-10-02).
2. bands = 5, b1 = brown, b2 = black, b3 = black, mult = brown, tol = brown gives resistance = 1 kΩ, ohms = 1,000, tolerance = 1%, min = 990 Ω, max = 1.01 kΩ. Source: IEC 60062:2016 Marking codes for resistors and capacitors, colour code table as given in “Electronic color code” (https://en.wikipedia.org/wiki/Electronic_color_code, retrieved 2026-10-02).
3. bands = 6, b1 = red, b2 = red, b3 = black, mult = gold, tol = blue, tc = brown gives resistance = 22 Ω, tolerance = 0.25%, min = 21.945 Ω, max = 22.055 Ω, tempco = 100. Source: IEC 60062:2016 Marking codes for resistors and capacitors, colour code table as given in “Electronic color code” (https://en.wikipedia.org/wiki/Electronic_color_code, retrieved 2026-10-02).
4. bands = 4, b1 = green, b2 = blue, mult = green, tol = none gives resistance = 5.6 MΩ, min = 4.48 MΩ, max = 6.72 MΩ. Source: IEC 60062:2016 Marking codes for resistors and capacitors, colour code table as given in “Electronic color code” (https://en.wikipedia.org/wiki/Electronic_color_code, retrieved 2026-10-02).

## FAQ

### How do I read a 4-band resistor?

The first two bands are digits, the third is the multiplier (a power of ten) and the fourth is the tolerance. Yellow (4), violet (7), red (×10²), gold (±5%) is 47 × 100 = 4,700 Ω, or 4.7 kΩ ± 5%.

### How do I read a 5-band or 6-band resistor?

The first three bands are digits, then the multiplier, then the tolerance. A sixth band gives the temperature coefficient. Brown, black, black, brown, brown is 100 × 10 = 1,000 Ω ± 1%.

### Which end do I start reading from?

Start from the band nearest an end. The tolerance band, often gold or silver, is usually set apart from the others. Gold and silver never come first, because they are not digits.

### What do gold and silver mean as the multiplier?

Gold multiplies by 0.1 and silver by 0.01, for resistances under 10 Ω. Red, red, gold is 22 × 0.1 = 2.2 Ω.

### What does tolerance mean?

How far the real resistance may be from the marked value. A 4.7 kΩ resistor at ±5% can be anywhere from 4,465 Ω to 4,935 Ω. With no tolerance band, it is ±20%.

### What is the temperature coefficient?

How much the resistance changes when the resistor warms up, in parts per million per kelvin. At 100 ppm/K, a 1,000 Ω resistor changes by 0.1 Ω for each degree.

## Sources

- IEC 60062:2016, Marking codes for resistors and capacitors (the colour code), as tabulated in “Electronic color code” (significant figures, multipliers pink ×10⁻³ to white ×10⁹, tolerances, temperature coefficients), retrieved 2026-10-02. https://en.wikipedia.org/wiki/Electronic_color_code
- IEC webstore, IEC 60062:2016 Marking codes for resistors and capacitors (the standard itself; the 2016 edition added pink for ×10⁻³), retrieved 2026-10-02. https://webstore.iec.ch/en/publication/25395