Turn the colored stripes on a resistor into a number. Pick 4, 5 or 6 bands and set each color, and the calculator reads them the way an engineer does: the first bands are significant digits, the next is a ×10 multiplier, then the tolerance, and — on a 6-band part — the temperature coefficient. See the resistance, the ± tolerance and the exact min-to-max range, with a color-coded resistor drawn live so you can match it to the one in your hand. It all runs on your device.
You are in the Physics lab.
How the bands become a value, and which end to start from.
The bands sit closer together at one end and leave a gap before the tolerance band at the other. Start reading from the grouped end. The gold or silver tolerance band is a giveaway — those colors only appear as a multiplier or tolerance, so the band nearest them is where you finish, not start.
The first two bands (three on a 5 or 6-band part) are significant digits using the color-to-number key. The next band is a power-of-ten multiplier — red is ×100, orange ×1 k, and gold and silver shrink the value by ×0.1 and ×0.01 for resistors under 10 Ω. The calculator multiplies them out exactly and shows the resistance in Ω, kΩ or MΩ.
The tolerance band says how far the real resistor may stray from its printed value. Gold is ±5%, brown ±1%, and the tighter colors go down to ±0.05%. The tool turns that into a concrete min-to-max range, so a 1 kΩ ±5% part shows as 950 Ω – 1,050 Ω. A 6-band resistor adds a temperature-coefficient band in ppm/K for how much it drifts when hot.
One color key, used three different ways.
The ten digits map to ten colors in spectral order: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. The mnemonic runs from dark to light. The same colors are reused for the multiplier and tolerance, which is why position — not just color — matters.
Line the digit bands up into a number, then multiply by ten to the power of the multiplier band. Brown-black-red is 10 × 10² = 1,000 Ω. On a 5 or 6-band resistor there are three digits for one more figure of precision, so brown-black-black-brown is 100 × 10 = 1,000 Ω with a tighter tolerance.
The tolerance band is a percent: gold ±5%, silver ±10%, brown ±1%, red ±2%, and finer colors below. It reflects manufacturing spread, so tighter tolerance parts cost more. The sixth band, present on precision resistors, is the temperature coefficient in ppm/K — 50 ppm/K means the resistance changes by 50 parts per million for each degree of temperature change. Our Ohm's law calculator puts that resistance to work.
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