Resistor Colour Code Calculator (4 & 5 Band)

Resistor Colour Code Guide

What's the key thing to understand about Reading the Bands?

Resistor colour codes encode resistance value, multiplier, and tolerance using coloured bands. Reading direction: tolerance band (gold/silver) is the LAST band. Hold resistor so this is on the right. Read from left to right. 4-band code: Band 1 = first digit. Band 2 = second digit. Band 3 = multiplier (×10^value). Band 4 = tolerance. 5-band code (more precise): Band 1 = first digit. Band 2 = second digit. Band 3 = third digit. Band 4 = multiplier. Band 5 = tolerance. Example 4-band: Yellow-Violet-Red-Gold reads as 4, 7, ×100, giving 4,700Ω (4.7kΩ) with ±5% tolerance.

What do I need to know about The Colour Code Memorised?

Colour values for digits: Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Grey=8, White=9. Mnemonic: 'Bad Boys Race Our Young Girls But Violet Generally Wins' or similar. Multiplier band uses same digit colours, plus Gold=×0.1 and Silver=×0.01 for small resistances. Tolerance colours: Brown=±1%, Red=±2%, Green=±0.5%, Blue=±0.25%, Violet=±0.1%, Grey=±0.05%, Gold=±5%, Silver=±10%, no band=±20%. Most common in hobbyist work: ±5% (gold) and ±1% (brown) tolerances. Reading reliably from a photo or in poor lighting can be tricky, which is why a multimeter is worth using to confirm the value on anything critical.

What should I know about Standard Values (E-Series)?

Resistors come in standard preferred values: E12 series (±10% tolerance, 12 values per decade): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82. Most common. E24 series (±5% tolerance, 24 values per decade): adds 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, 91. Hobbyist standard. E48 (±2%): adds intermediate values. E96 (±1%): finer increments for precision work. Common multipliers: ×1 (1Ω-99Ω), ×10 (100Ω-990Ω), ×100 (1kΩ-9.9kΩ), ×1k (10kΩ-99kΩ), ×10k (100kΩ-990kΩ), ×100k (1MΩ-9.9MΩ). Why standard values exist at all: manufacturing every conceivable resistance would be impractical, so a standardised, evenly log-spaced set of preferred values covers the full range with predictable tolerance gaps between them.

What's the key thing to understand about Special Cases?

Single black band (sometimes): 0Ω 'jumper' resistor — used to make PCB rework simpler. 4-band zero ohm: Black-Black-Black-(any tolerance) = 0Ω. Failure modes: open circuit (infinite resistance) — most common failure. Short circuit (zero resistance) — rare. Wrong value due to manufacturing defect or mis-read. Burned: visible discoloration from excess power dissipation. Resistor power rating: in addition to colour-coded value, resistors have power ratings (1/8W, 1/4W, 1/2W, 1W, 5W, 10W, etc.). Standard power ratings correspond to physical resistor size — a bigger resistor body can dissipate more heat before failing, which is why higher-wattage resistors are noticeably larger.