Resistor Color Code Calculator - Decode EIA Color Bands

A resistor color code calculator decodes the colored bands printed on a through-hole resistor into a resistance in ohms, kΩ, MΩ, or GΩ, with the tolerance range and the temperature coefficient on six-band parts included. It also works in reverse: write a color sequence for a target resistance.

• • Decode a resistor from a parts bin: Read the bands and see the nominal resistance with the tolerance range.
• • Order a resistor for a target value: Encode a target resistance in kΩ or MΩ into a color sequence for a parts order.
• • Check tolerance acceptance for a circuit: Read the min and max bounds so a part fits a design window.
• • Decode precision parts with temperature drift: Use 6-band mode for ±1% parts with a ppm/°C temperature coefficient.

Through-hole resistors are too small to print a numeric value, so the EIA standard encodes the value as colored bands. Red-red-brown-gold decodes to 220 Ω with ±5% tolerance, and the calculator can encode a target value back into a band sequence.

Once you decode a resistance with the resistor color code calculator, the Ohm's Law calculator lets you drop the value into V = IR to size the surrounding circuit.

The calculator looks up each color in the EIA color table, concatenates the digit bands into a number, and multiplies by the multiplier. The tolerance band gives the accepted range, and a sixth band adds the temperature coefficient on precision parts.

• D1, D2, D3: Digit bands, each color maps to a digit from 0 (black) through 9 (white).
• Multiplier (M): Power-of-ten multiplier. Black is ×1, brown ×10, gold ×0.1, silver ×0.01.
• Tolerance (tol): Accepted deviation as a percentage. Gold (±5%) is the most common consumer value.
• Temperature coefficient (TC): Sixth-band drift rate in ppm/°C. Brown (100), red (50), orange 15, yellow 25, blue 10, violet 5.

For five-band and six-band parts the formula gains a third significant digit, which is why those parts usually carry a 1% or better tolerance. In encode mode the calculator picks the smallest power-of-ten multiplier that lets the value sit in a two- or three-digit mantissa range.

According to Wikipedia Electronic color code, a through-hole resistor is marked with two (4-band) or three (5/6-band) digit color bands followed by a multiplier band, a tolerance band, and an optional temperature coefficient band, so red-red-brown-gold decodes to 22 × 10^1 = 220 Ω with gold (±5%) tolerance.

Resistors and capacitors sit in the same RC timing and filter networks, so the capacitor calculator decodes the matching component for the same schematic.

Four ideas cover the EIA color code; learn these once and decoding becomes mechanical.

The decoded resistance is the R in an RC low-pass or high-pass filter, and the capacitive reactance calculator returns the matching Xc at any chosen frequency.

Five steps take you from a resistor in your hand (or a target value) to a complete resistance, tolerance range, and color sequence.

1. 1 Pick decode or encode mode: Use Decode to read a printed color sequence into ohms, or Encode to write a sequence for a target resistance.
2. 2 Choose the band count: Pick 4 for a typical consumer part, 5 for a precision ±1% part, or 6 when the part also lists a temperature coefficient.
3. 3 Match each band to its color: Hold the resistor with the tolerance band on the right, then read each band left to right and select the matching color.
4. 4 Set the tolerance band: Pick the rightmost band color. If there is no tolerance band, choose 'No band = ±20%' for the IEC 60062 default.
5. 5 Read the result panel: Check the nominal resistance in the auto-selected prefix, the tolerance range, and the temperature coefficient on six-band parts.

A parts bin has a four-band resistor with red, red, brown, gold stripes. Pick Decode, set Band Count to 4, Band 1 to red, Band 2 to red, Multiplier to brown, and Tolerance to gold. The result panel shows 220 Ω with a tolerance range of 209 Ω to 231 Ω.

When you need the inverse relationship between conductance and the decoded resistance value, conductivity to resistivity calculator solves the σ to ρ conversion from the same physics.

Six practical benefits of one resistor color code calculator over a printed color chart and a separate tolerance table.

• • Decode and encode in one tool: Switches between reading a printed color sequence and writing a sequence for a target resistance.
• • Covers 4-band, 5-band, and 6-band parts: Handles the full EIA range from a consumer four-band part to a precision six-band part with temperature coefficient.
• • Auto-selected prefix for readability: Reads the result in the SI prefix that keeps the printed number between 1 and 999, so 4,700 Ω shows as 4.7 kΩ.
• • Shows the tolerance range: Reports the min and max resistance from the tolerance band so the part can be confirmed against a design window.
• • Encodes back to color bands: Writes a fresh color sequence for a target resistance in kΩ or MΩ with the digit and multiplier colors already in order.
• • Includes gold and silver multipliers: Decodes the ×0.1 gold and ×0.01 silver multipliers used on sub-10 Ω resistors without a separate lookup.

Encoding is the harder direction because it requires choosing a multiplier exponent and matching the mantissa to the EIA color order; the calculator handles that step so the result lands on a real part number.

When the decoded value lands in a prefix the rest of the design does not use, the electrical resistance calculator converts ohms, kilohms, megohms, and gigohms in both directions.

Five factors decide whether the decoded value matches the part on the bench; two limitations describe when the calculator is incomplete.

• • The calculator assumes the resistor is ideal, with no parasitic inductance or parallel capacitance. High-frequency analog work needs a separate impedance analysis.
• • Encoding snaps to the nearest mantissa the band count allows, so the encoded value may differ from the target by up to a few percent.

Reading the resistor in good lighting with a magnifier helps when bands are faded or close in color.

According to Digi-Key Resistor Color Code Calculator, a six-band resistor adds a temperature coefficient on the sixth band in ppm/°C, with brown equal to 100, red equal to 50, orange 15, yellow 25, blue 10, and violet 5 ppm/°C.

According to Wikipedia IEC 60062, the international resistor and capacitor marking standard specifies that a missing tolerance band on a through-hole resistor defaults to ±20%, which is why the calculator's 'No band' option returns a 20% range.

Filter design pairs the decoded resistor with combined capacitance, and the capacitors in series calculator handles the reciprocal-sum equivalent for stacked parts.