Resistor Color Code Calculator

Resistor Color Code Calculator

Resistor Color Code Calculator — Decode & Encode Color Bands

Resistors use color-coded bands printed on their bodies to indicate resistance values and tolerances. This free resistor color code calculator lets you decode 4-band and 5-band resistors to find their resistance value, or enter a resistance value to see which color bands represent it. It's an indispensable reference for anyone building, testing, or repairing electronic circuits.

How to Read Resistor Color Codes

For a 4-band resistor: the first two bands are significant digits, the third band is the multiplier, and the fourth band is the tolerance. For a 5-band resistor (more precise, typically 1% tolerance): the first three bands are significant digits, the fourth is the multiplier, and the fifth is the tolerance. The color sequence from left to right always starts at the end closest to the first significant digit band.

Color Code Mnemonic

A classic mnemonic to remember the color order (Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White) is: "BB ROY of Great Britain has a Very Good Wife." Each first letter corresponds to a color and a digit 0–9.

Multiplier and Tolerance Bands

Gold and Silver bands only appear as multiplier (×0.1 and ×0.01) or tolerance bands (±5% and ±10%). They are never used as digit bands. A resistor with no tolerance band is assumed to have ±20% tolerance.

Practical Tips

  • Hold the resistor so the tolerance band (gold or silver) is on the right — the remaining bands read left to right give digits and multiplier.
  • 5-band resistors with brown or red tolerance bands are precision resistors — check carefully against the standard color band positions.
  • If unsure of band count, use a multimeter to verify the actual value.

Frequently Asked Questions

How do I tell which end of the resistor to start reading from?
The tolerance band (gold or silver) is always at one end. Start reading from the opposite end. If the gap between the last two bands is larger than the others, that wider gap marks the tolerance band side.
What does the tolerance band mean?
Tolerance indicates how much the actual resistance may vary from the marked value. A 1 kΩ ±5% resistor may be anywhere from 950 Ω to 1050 Ω. For critical circuits, use 1% or better precision resistors.
Are 5-band resistors more accurate than 4-band?
Yes. 5-band resistors provide three significant digits instead of two, allowing tolerances of 1% or 2%. They are common in precision analog circuits, instrumentation, and audio equipment.
Why are some resistors blue-bodied?
Blue-bodied resistors are typically metal film types, which offer better temperature stability and lower noise than the standard brown-bodied carbon film resistors. The body color does not affect the color code reading.
What is an E12 or E24 series resistor?
E12 and E24 are standard resistor value series. E12 has 12 preferred values per decade (for ±10% tolerance) and E24 has 24 values (for ±5%). Standard values are spaced so that any resistance falls within tolerance of a neighboring standard value.