A 4-band resistor colour code calculator translates the painted bands on a through-hole resistor into its ohmic value and tolerance. The formula is strictly sequential: Band 1 (first significant digit), Band 2 (second significant digit), Band 3 (multiplier), and Band 4 (tolerance). For example, a resistor with Brown (1), Black (0), Red (x100), and Gold (±5%) bands equals 10 x 100 = 1,000Ω (1kΩ) with a 5% tolerance.
Unlike wire color codes, which fracture into regional standards, resistor codes are universally standardized. Below is the definitive reference table to verify your calculations or build your own mental lookup.
The Complete 4-Band Resistor Colour Code Reference Table
This table follows the IEC 60062 international standard. Read the bands from left to right, starting from the end where the bands are grouped closest together, leaving the wider-spaced tolerance band on the right.
| Colour | Band 1 (1st Digit) | Band 2 (2nd Digit) | Band 3 (Multiplier) | Band 4 (Tolerance) |
|---|---|---|---|---|
| Black | - | 0 | x1 (10^0) | - |
| Brown | 1 | 1 | x10 (10^1) | ±1% (F) |
| Red | 2 | 2 | x100 (10^2) | ±2% (G) |
| Orange | 3 | 3 | x1k (10^3) | - |
| Yellow | 4 | 4 | x10k (10^4) | - |
| Green | 5 | 5 | x100k (10^5) | ±0.5% (D) |
| Blue | 6 | 6 | x1M (10^6) | ±0.25% (C) |
| Violet | 7 | 7 | x10M (10^7) | ±0.1% (B) |
| Grey | 8 | 8 | x100M (10^8) | ±0.05% (A) |
| White | 9 | 9 | x1G (10^9) | - |
| Gold | - | - | x0.1 (10^-1) | ±5% (J) |
| Silver | - | - | x0.01 (10^-2) | ±10% (K) |
Standard Variants and the 'Rows People Get Wrong'
When makers ask about regional variants like NEC (US) vs. IEC 60446 (EU/UK) vs. old UK wiring colors, they are confusing wire insulation standards with component marking standards. Resistor color codes do not have regional variants; they are governed globally by IEC 60062:2016. A brown-black-red-gold resistor means 1kΩ whether you bought it in Tokyo, Berlin, or Chicago. However, because hobbyists frequently mix up wire and component logic, misinterpreting the table is common.
The Rows People Get Wrong
- Gold and Silver as Multipliers (Band 3): Beginners often assume Gold and Silver only apply to tolerance. When used as a multiplier, Gold means divide by 10 (x0.1) and Silver means divide by 100 (x0.01). A Yellow-Violet-Gold-Gold resistor is 47 x 0.1 = 4.7Ω ±5%.
- Black as a Multiplier (Band 3): A Black multiplier does not mean the resistance is zero. It means multiply by 10^0 (which is 1). A Brown-Black-Black-Gold resistor is 10 x 1 = 10Ω ±5%.
- Red vs. Orange under Poor Lighting: Under warm 2700K workshop LEDs, Red (2) and Orange (3) look nearly identical. If you are calculating a bias network for a transistor and your circuit is behaving erratically, pull the resistor and check it under 5000K daylight-balanced light or just use your multimeter.
Safe Interpretation When Markings Are Faded or Burnt
Carbon film and metal film resistors degrade when subjected to thermal overstress. If a 1/4W resistor dissipates 1W due to a fault, the phenolic or epoxy coating will blister, and the color bands will scorch into a uniform muddy brown or black.
The Verification Protocol:
- Isolate the Component: Desolder at least one leg of the resistor from the PCB. Measuring in-circuit will yield false lows due to parallel current paths through other components.
- Zero Your DMM: Short your digital multimeter probes together. Subtract this lead resistance (usually 0.1Ω to 0.4Ω) from your final reading, especially critical for resistors under 10Ω.
- Check the Tolerance Window: If the faded bands suggest a 1kΩ resistor with a Gold (±5%) band, the acceptable range is 950Ω to 1050Ω. If your DMM reads 1120Ω, the carbon track has permanently degraded. Replace it.
Frequently Asked Questions
How does a 4 band resistor colour code calculator handle gold and silver multipliers?
A robust calculator shifts the decimal point to the left instead of adding zeros. For Band 1 = Green (5), Band 2 = Blue (6), and Band 3 = Silver (x0.01), the calculator computes 56 x 0.01 = 0.56Ω. This is commonly used for current-sense shunt resistors in power supplies. If your calculator does not support decimal multipliers, it is poorly programmed; use the formula manually.
Why is my 4 band resistor colour code calculator giving a different value than my multimeter?
Calculators output the nominal value, while your multimeter measures the actual value. A calculator will tell you Red-Red-Brown-Gold is exactly 220Ω. However, because of the Gold (±5%) tolerance band, the physical resistor can legally measure anywhere between 209Ω and 231Ω right off the factory tape. Furthermore, cheap multimeters can have a ±1% basic DC accuracy error. Always trust a verified in-circuit-isolated DMM reading over the nominal color code for precision analog design.
Can I use a 4 band resistor colour code calculator for 5-band precision resistors?
No. A 5-band resistor (common in 1% metal film E96 series parts) adds a third significant digit before the multiplier. For example, a 5-band Brown-Black-Black-Red-Brown resistor is 100 x 100 = 10,000Ω (10kΩ) ±1%. If you force this into a 4-band calculator, it will read Brown(1)-Black(0)-Black(x1)-Red(±2%), yielding a completely incorrect 10Ω ±2%. Always count the physical bands before selecting your calculator mode.
Which way do I read the bands if there is no obvious spacing gap?
Manufacturers usually leave a wider gap between the multiplier and the tolerance band, or print the tolerance band (Gold/Silver) slightly thicker. If the spacing is ambiguous, look for a Gold or Silver band—these are never used as significant digits (Bands 1 or 2) in standard E24 values. Therefore, if you see a Gold band on one end, that end must be the right side (Band 4), meaning you read from the opposite end. If neither end is Gold/Silver, calculate the value both ways and check which result aligns with standard E-series preferred values (e.g., 47kΩ is standard; 74kΩ is not).
