Six-band resistor color code calculator with temperature coefficient

Enter all six color names in reading order and this calculator returns the exact resistance in ohms, tolerance percentage, and ppm/°C rating without rounding or guessing from a preferred-value series.

Read the six bands in the correct direction

Begin at the end where the colored bands are grouped most closely, leaving the temperature coefficient band last. On a six-band resistor, bands one through three are significant digits. Black represents zero, brown one, red two, and the sequence continues through white for nine. The fourth band is the multiplier, the fifth is tolerance, and the sixth is temperature coefficient. Orientation matters because the same color can mean a digit, a power-of-ten multiplier, a percentage, or a ppm rating depending on its position. If the physical spacing is difficult to see, look for the tolerance and temperature colors: gold or silver can be a tolerance band but cannot be a significant digit, while common temperature coefficient colors include brown, red, orange, yellow, blue, violet, and grey. Enter color names from left to right. The calculator accepts either “grey” or “gray,” normalizes capitalization and surrounding spaces, and reports an error when a color is not valid for its particular position rather than silently inventing a value.

Understand resistance and tolerance

The first three bands are joined as a three-digit significant value. For example, brown, black, black produces 100. The multiplier band then applies a decimal power: red means ten squared, so 100 becomes 10,000 ohms. Gold and silver multipliers support low-value precision resistors by moving the decimal point left one or two places. The returned resistance is an exact decimal string in ohms, which avoids scientific notation and floating-point artifacts. The tolerance band gives the permitted manufacturing deviation around that nominal resistance. Brown is ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1%, grey ±0.05%, gold ±5%, and silver ±10%. A 10,000-ohm resistor with a brown tolerance band is therefore specified within one percent of nominal under the conditions stated by its manufacturer. Tolerance is not measurement uncertainty and does not predict every operating effect; self-heating, aging, applied voltage, and circuit conditions can move the observed value. Use the decoded percentage as a component specification, then consult the part datasheet when a design depends on tighter real-world behavior.

Use the temperature coefficient rating

The sixth band expresses temperature coefficient in parts per million per degree Celsius, commonly written ppm/°C. Brown means 100 ppm/°C, red 50, orange 15, yellow 25, blue 10, violet 5, and grey 1. This rating estimates how strongly resistance changes as component temperature moves away from its reference temperature. A 10,000-ohm resistor rated at 50 ppm/°C changes by approximately 10,000 × 50 / 1,000,000, or 0.5 ohm, for each degree Celsius of temperature difference. Across 20°C, that first-order estimate becomes 10 ohms. The coefficient may describe a maximum magnitude rather than a guaranteed signed slope, so the color alone does not tell you whether resistance rises or falls. It also does not replace the manufacturer’s temperature range, drift, power derating, or long-term stability data. The decoded ppm value is particularly useful when comparing parts for precision dividers, instrumentation, references, and sensor interfaces. For automated use, the API charges $0.002 per request and returns normalized bands alongside each computed field, making results straightforward to validate and store.