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About This Calculator
Resistors use colored bands to indicate their resistance value, tolerance, and sometimes temperature coefficient. Reading these bands correctly requires memorizing a specific color-to-digit mapping that many engineers find easy to confuse. This calculator decodes 4-band, 5-band, and 6-band resistors instantly, eliminating guesswork from circuit assembly and repair.
Quick Tips
- 1 The mnemonic "BB ROY of Great Britain has Very Good Wife" gives the color order.
- 2 Gold tolerance band means +/-5%; silver means +/-10%; no band means +/-20%.
- 3 The last color band before tolerance is the multiplier (number of zeros).
Example Calculation
Resistor bands: Brown, Black, Orange, Gold.
Resistance: 10,000 ohm (10k ohm) | Tolerance: +/-5% | Range: 9,500-10,500 ohm
How to Read Resistor Color Codes
A 4-band resistor has two digit bands, one multiplier band, and one tolerance band. Read from the band closest to one end. The first two bands give a two-digit number, the third band multiplies it, and the fourth band shows the tolerance percentage.
Color Code Chart
Digit colors: Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Gray=8, White=9. Multiplier adds zeros: Brown=x10, Red=x100, Orange=x1K, etc. Gold and Silver multipliers divide: Gold=x0.1, Silver=x0.01.
Tolerance Explained
Tolerance indicates how much the actual resistance may vary from the stated value. A 1K ohm resistor with 5% tolerance (gold band) can range from 950 to 1,050 ohms. Tighter tolerances cost more but provide more precise resistance values.
Standard Resistor Values
Resistors come in standard values from the E-series. E12 (10% tolerance) has 12 values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. E24 (5%) has 24 values. E96 (1%) has 96 values per decade for finer precision.
Frequently Asked Questions
The tolerance band (gold, silver, or wider gap) is always on the right end. Start reading from the opposite end. If there is no tolerance band (20%), the bands are usually grouped closer to one end, which is the starting end.
Gold band (5%) is the most common tolerance for general-purpose resistors. For precision applications, 1% (brown band) resistors are standard. Wider tolerances (10% silver, 20% none) are less common in modern electronics.
Five-band resistors have three digit bands, one multiplier, and one tolerance band for higher precision. Six-band resistors add a temperature coefficient band. This calculator handles standard 4-band resistors.
Color bands are visible from any angle and do not wear off like printed text. They work on cylindrical components where text might be hard to read. The system dates back to the 1920s when printing small text on tiny components was impractical.