Pick the colors on your resistor to read its resistance and tolerance, or type a value such as 4.7k and get its color bands. A live drawing shows the resistor as you change the bands.
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On a 4-band resistor, the first two bands are digits, the third is a power-of-ten multiplier and the fourth is the tolerance. Precision 5-band resistors have three digit bands before the multiplier. 6-band resistors add a final band for the temperature coefficient in parts per million per kelvin. The digit colors run black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8 and white 9. Gold and silver as multipliers mean ×0.1 and ×0.01. For example, yellow-violet-red-gold is 47 × 100 = 4,700 Ω, or 4.7 kΩ, with ±5% tolerance.
The tolerance band (often gold or silver) is usually set slightly apart from the others. Start reading from the opposite end.
Schematics often write the decimal point as a letter: 4R7 is 4.7 Ω, 4k7 is 4.7 kΩ and 1M5 is 1.5 MΩ. The reverse lookup understands this format.
Digit, digit, multiplier, tolerance. Red-red-brown-gold means 22 × 10 = 220 Ω ±5%.
It's the temperature coefficient, which is how much the resistance changes per degree of temperature change, in ppm/K. Brown is 100 ppm/K.
The reverse lookup rounds to the nearest value the chosen band count can show and tells you when rounding happened. Switch to 5 bands for three significant digits.
Yes. The reverse lookup accepts plain numbers (4700), suffixes (4.7k, 1M) and letter-as-decimal notation (4k7, 4R7, 2M2).
It's how far the actual resistance may differ from the marked value. The calculator shows the resulting minimum and maximum.
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