Resistor Color Code Calculator — 4, 5 and 6-band decoder with live drawing

Real-world use cases

• Read a bag of unlabeled salvage resistors

  You pulled a handful of resistors off a dead board and they came with no markings beyond the stripes. Set the band count to 4, pick the colors off each part, and sort them into bins by value — 1 kΩ here, 10 kΩ there. The on-screen drawing lets you confirm you read the stripes in the right order before you commit a part to your tidy new parts drawer.

• Spec a current-limiting resistor for an LED

  Your Arduino project drives an LED and you calculated you need about 330 Ω. Switch to reverse mode, type 330, leave tolerance at ±5%, and the tool draws orange-orange-brown-gold — the exact stripes to look for in your parts bin. No standard part is made at, say, 312 Ω, so the snap to the nearest E24 value saves you hunting for one that does not exist.

• Grade an electronics lab worksheet

  A student lab asks learners to identify ten resistors by color. As the instructor you decode each one here to build the answer key, including a 5-band 1% part where the third digit matters. Because the tool shows the tolerance and (on 6-band parts) the temperature coefficient too, you can mark the harder questions where students must distinguish a brown tolerance band from a brown digit band.

• Double-check a precision divider resistor

  You are building a voltage reference and the divider calls for a 4.99 kΩ 1% resistor. The five stripes read yellow-white-white-brown-brown. Decode them on a 5-band setting to confirm you grabbed 4.99 kΩ and not 49.9 kΩ — an easy off-by-a-decade mistake when the multiplier band is a subtle shade — before you solder it into a circuit where the value sets your reference voltage.

• Teach yourself the color code with the drawing

  Brand new to electronics? Toggle colors one band at a time and watch the resistance number and the painted stripe both change. Set the first band to brown and the value's leading digit becomes 1; bump the multiplier from red to orange and watch 1 kΩ jump to 10 kΩ. Seeing the picture move with the number builds the mental model far faster than memorizing "Bad Beer Rots Our Young Guts" mnemonics.

Common pitfalls

• Reading the resistor backwards. The first band is never gold, silver, or black — if your leftmost stripe is one of those, flip the part around so the tolerance band sits on the right.

• Confusing the multiplier band with a digit band. On a 4-band part the third stripe is a power-of-ten multiplier, not a third digit; red as a multiplier means ×100, not the digit 2.

• Mixing up a 5-band reading on a 4-band part (or vice versa). A wrong band count shifts every role by one and gives a value off by a decade or more — set the band count to match the stripes you actually see first.

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