Resistor Colourcode Decoder Tool: Fast, Accurate, and Free

How to Use a Resistor Colourcode Decoder: Step-by-Step GuideResistors are one of the most common components in electronic circuits. They control current, set voltage levels, and form part of filters and timing networks. To use resistors correctly you must know their resistance value, which is often encoded on their bodies using colour bands. A resistor colourcode decoder (tool or chart) makes reading these values fast and reliable. This guide walks you through understanding resistor colour codes, using a decoder for different band types (4-, 5-, and 6-band resistors), and practical tips for real-world work.

Basic principles of resistor colour codes

Each colour represents a number or multiplier, and sometimes a tolerance or temperature coefficient. The standard colour-to-number mapping is:

• Black = 0
• Brown = 1
• Red = 2
• Orange = 3
• Yellow = 4
• Green = 5
• Blue = 6
• Violet = 7
• Grey = 8
• White = 9

Multipliers use the same colours but represent powers of ten (for example, Red multiplier = ×10^2 = 100). Tolerance bands are typically gold, silver, or brown/green for tighter tolerances.

Resistor band types overview

• 4-band: Two significant digits, multiplier, tolerance. Common for many general-purpose resistors.
• 5-band: Three significant digits, multiplier, tolerance. Used for higher precision values.
• 6-band: Same as 5-band plus a sixth band for temperature coefficient (ppm/°C). Used in precision/high-stability resistors.

Step-by-step: using a resistor colourcode decoder (4-band)

1. Identify the end: Hold the resistor so the tolerance band (gold, silver, brown, etc.) is on the right. The tolerance band is usually slightly separated from the others.
2. Read the first two bands from left to right — these are the significant digits. Convert colours to digits using the mapping above.
3. Read the third band — the multiplier. Convert the colour to a power of ten. Multiply the two-digit number by this multiplier.
4. Read the fourth band — tolerance (e.g., gold = ±5%, silver = ±10%, brown = ±1%).
5. Example: Bands = Yellow, Violet, Red, Gold → 4 (yellow) 7 (violet) ×10^2 (red) = 47 × 100 = 4.7 kΩ ±5%.

Step-by-step: using a resistor colourcode decoder (5-band)

1. Orient the resistor so the tolerance band is on the right.
2. Read the first three bands — these are the three significant digits.
3. Read the fourth band — multiplier. Multiply the three-digit number by the multiplier.
4. Read the fifth band — tolerance.
5. Example: Bands = Brown, Black, Black, Orange, Brown → 1 0 0 ×10^3 = 100 × 1000 = 100 kΩ ±1%.

Step-by-step: using a resistor colourcode decoder (6-band)

1. Find the tolerance band and orient the resistor accordingly.
2. Read the first three bands for significant digits, the fourth band for multiplier, the fifth for tolerance, and the sixth for temperature coefficient (ppm/°C).
3. Example: Bands = Brown, Black, Black, Red, Brown, Brown → 1 0 0 ×10^2 = 100 × 100 = 10 kΩ ±1%, 100 ppm/°C.

Using an online or handheld decoder tool

• Input or select the colours in order; the tool will display the resistance, tolerance, and sometimes temperature coefficient.
• Advantages: removes manual errors, useful for faded bands, supports different band counts.
• Tip: if bands are faded, compare against the chart or use a multimeter to confirm.

Common pitfalls and tips

• Some resistors use a body-dot or end-dot for orientation; always verify which side corresponds to the tolerance band.
• Colour shades (e.g., brown vs. red) can be confusing under poor light — use good lighting or magnification.
• Zero-ohm resistors are marked with a single black band (a jumper).
• For surface-mount resistors (SMD), read the printed numeric code instead of colour bands.

Quick reference: common tolerance colours

• Brown = ±1%
• Red = ±2%
• Gold = ±5%
• Silver = ±10%
• No band = ±20%

Practice examples

1. Green, Blue, Orange, Gold → 5 6 ×10^3 = 56 kΩ ±5%
2. Red, Red, Brown, Brown, Brown → 2 2 1 ×10^1 = 221 × 10 = 2.21 kΩ ±1% (5-band)
3. Black, Brown, Black, Brown → 0 1 ×10^1 = 1 Ω ±1% (watch orientation)

When to verify with a multimeter

Always measure when working in precision circuits, when colour bands are damaged/faded, or when the resistor value critically affects circuit function.

Using a resistor colourcode decoder saves time and reduces errors. With practice you’ll read bands quickly and confirm values when precision matters.