How to read a resistor
Small resistors are marked with colored bands instead of numbers. Hold the resistor with the tolerance band (often gold or silver, set a little apart from the others) on the right. On a 4-band resistor, the first two bands are digits, the third is a multiplier and the fourth is the tolerance. On a 5-band resistor, the first three bands are digits, then the multiplier and the tolerance. The digit colors are black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8 and white 9. Choose each band’s color from the lists and the tool shows the resistance, with the range it could really fall in.
Multipliers and tolerance
The multiplier band says how many zeros to add: brown is ×10, red ×100, orange ×1,000 (so yellow, violet, orange is 47,000 ohms), and so on up to white at ×1,000,000,000. Gold and silver as multipliers mean ×0.1 and ×0.01, for values below 10 ohms. The tolerance band tells how far the real value may be from the marked one: gold ±5%, silver ±10%, brown ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1% and grey ±0.05%. A resistor with no tolerance band is ±20%. Precision resistors, with ±1% or better, usually have five bands.
Questions
How do I find the bands for a value? Use the second tab: type the resistance and the tolerance, and the bands to look for are drawn. A 4-band resistor can only hold two significant digits (4.7 kΩ, not 4.75 kΩ); use 5 bands for three. What about 6-band resistors? The sixth band is a temperature coefficient, which this tool leaves out. The colors look alike on my resistor. Check with a multimeter, since brown, red and orange are easy to confuse in poor light. For the electrical sums, use the Ohm’s Law Calculator.