Georg Simon Ohm, a German physicist, demonstrated proportionality between current and voltage, thus defining resistance (this rule was named after him as Ohm's law).
But how can we tell the value of a resistor we have just in front of us?
Whoever takes care of electronic assemblies knows by heart the resistor color codes, but for
those that are starting from the very beginning ( and, why not, for the elder ones :)) it is a bit difficult to remember color codes.

• Calculate Resistor Values from Color Codes (the best)
• Resistor value calc (it seems a clone of the previous one, useful as mirror)
• Resistor Color Code Guide (a broader view of codes)
• Band Based Resistor Color Codes (4 - 5 - 6 bands)
• Resistor Color Code Table And Calculator (this is interactive as well)
• Electronic color code ("official" version)
• Codice colori resistenze (in Italian)

Save in your bookmarks one of these sites or this very page to use when you need to know a resistor value using color codes.

Buy now Resistors download free Datasheet from Farnell (24h delivery).