Resistor Color Decoder

What is a resistor color code?

Resistors use colored bands to indicate their resistance value, tolerance, and sometimes temperature coefficient. The system was standardized because resistors are too small for printed numbers to be reliably readable. Each color represents a digit (0–9) and the bands are read in sequence: significant digits, multiplier, and tolerance.

Four-band resistors are the most common: two digit bands, one multiplier, one tolerance. Five-band resistors add a third digit for greater precision (used in 1% and 0.1% tolerance resistors). Six-band resistors include a temperature coefficient band. The color sequence is: black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9.

4-band, 5-band, and 6-band resistors

The most widely used resistor in hobby and consumer electronics is the 4-band type. Reading left to right, the first two bands are significant digit bands (each representing one digit, 0 through 9). The third band is the multiplier — it sets the power of ten you multiply the two-digit number by. The fourth and final band indicates the tolerance of the component.

5-band resistors follow the same logic but squeeze in a third significant digit before the multiplier. This gives you three digits of precision instead of two, so a 5-band resistor can specify values like 1.00 kΩ rather than just 1.0 kΩ. You will find 5-band codes on precision resistors rated at ±1%, ±0.5%, or tighter.

6-band resistors add a sixth band at the far right end for the temperature coefficient (tempco), expressed in parts per million per degree Celsius (ppm/°C). Brown (100 ppm/°C), red (50 ppm/°C), and orange (15 ppm/°C) are the common tempco bands. If you need a stable resistance over a wide temperature range — for example in a precision audio circuit or a reference voltage divider — select a resistor with the lowest tempco you can afford.

The complete color-to-digit mapping

Every band color maps to a fixed digit and multiplier. Memorizing the table is worthwhile for anyone who works with through-hole components regularly. A popular mnemonic is: "B B ROY Great Britain Very Good Wife" — Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White — mapping to 0 through 9.

Gold and silver only appear in the multiplier and tolerance positions. As a multiplier, gold means ×0.1 (used for sub-ohm resistors), and silver means ×0.01. As a tolerance band, gold indicates ±5% and silver indicates ±10%. A bare resistor end with no tolerance band at all means ±20%, a specification you rarely see outside vintage equipment.

Worked decoding examples

Example 1 — 4-band: Brown · Black · Red · Gold. Brown = 1, Black = 0 → two-digit number 10. Red multiplier = ×100. 10 × 100 = 1,000 Ω = 1 kΩ. Gold tolerance = ±5%. The actual resistance lies anywhere from 950 Ω to 1,050 Ω.

Example 2 — 4-band: Yellow · Violet · Orange · Gold. Yellow = 4, Violet = 7 → 47. Orange multiplier = ×1,000. 47 × 1,000 = 47,000 Ω = 47 kΩ ±5%. This is one of the most commonly stocked values.

Example 3 — 5-band: Red · Red · Black · Black · Brown. Red = 2, Red = 2, Black = 0 → three-digit number 220. Black multiplier = ×1. 220 × 1 = 220 Ω. Brown tolerance = ±1%.

Example 4 — 5-band: Orange · Orange · Black · Red · Brown. Orange = 3, Orange = 3, Black = 0 → 330. Red multiplier = ×100. 330 × 100 = 33,000 Ω = 33 kΩ ±1%.

E-series preferred values

Resistors are not manufactured in every possible value. Instead, they follow standardized E-series sequences defined by IEC 60063. The E12 series provides 12 values per decade (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82) and pairs with ±10% tolerance. The E24 series doubles that density (24 values per decade) for use with ±5% components. E48 and E96 series cover ±2% and ±1% precision resistors respectively.

The idea behind E-series is that adjacent values overlap when their tolerance ranges are taken into account, so no value in the actual resistance spectrum goes uncovered. When selecting a resistor for a design, always choose the nearest standard E-series value — there is no point specifying 1,100 Ω when 1,000 Ω (1 kΩ) or 1,200 Ω are the real options on a supplier's shelf.

How to read resistor bands

Start from the band closest to one end of the resistor. Read the first two (or three) bands as digits. The next band is the multiplier — it tells you how many zeros to add. The last band is the tolerance. Example: brown-black-red-gold = 1, 0, x100 = 1,000 ohms (1K) with 5% tolerance.

Common mistakes when reading color codes

• Reading from the wrong end — Always find the tolerance band (gold or silver) first; it marks the right-hand end. Read the digits from left to right, away from the tolerance band.
• Confusing gold and yellow — Gold is a metallic, dull sheen; yellow is a bright, flat color. Gold only appears in the multiplier and tolerance positions, never as a digit band.
• Confusing silver and grey — Silver is a metallic finish used for ×0.01 or ±10%; grey is a flat matte color representing the digit 8.
• Misidentifying brown and red on aged components — Component leads oxidize and the body can yellow with heat. Hold the resistor up to a neutral light source; brown has a distinctly warm earth tone while red is clearly reddish.
• Ignoring the gap — On 5-band resistors the tolerance band is usually set slightly apart from the four digit+multiplier bands. If you see an even gap before the last band, that band is the tolerance.

Tolerance bands explained

• Gold = 5% — The most common tolerance for general-purpose resistors.
• Silver = 10% — Lower precision, used in non-critical applications.
• Brown = 1% — Precision resistors for accurate circuits.
• No band = 20% — Older or very cheap resistors.

How to use this tool

Select the color for each band using the visual color picker. Choose between 4-band, 5-band, or 6-band mode. The decoded resistance value appears instantly with the tolerance range. You can also enter a resistance value to see the expected color code.

Frequently asked questions

Which end do I start reading from?

The tolerance band (gold or silver) is always at the end. Start reading from the opposite end. If there is no gold or silver band, the first band is usually closer to one end of the resistor body. With 5-band resistors, the tolerance band has a wider gap before it.

Why not just print the value on the resistor?

Some modern resistors do print the value, especially larger power resistors. But standard 1/4-watt resistors are very small (about 6mm long), and printed text would be nearly impossible to read, especially after soldering. Color bands are visible from any angle and do not wear off. SMD resistors use printed numeric codes instead.

What is the difference between 5% and 1% resistors?

A 1 kΩ ±5% resistor will measure anywhere from 950 Ω to 1,050 Ω. A 1 kΩ ±1% resistor is guaranteed within 990 Ω to 1,010 Ω. For most general-purpose circuits — LED current limiting, pull-up/pull-down lines, debounce networks — ±5% is more than adequate and cheaper. Precision applications like op-amp gain networks, ADC reference dividers, or bridge circuits benefit from ±1% or tighter.

Can I use this tool for SMD resistors?

Surface-mount (SMD) resistors use a different coding system: a 3-digit or 4-digit numerical code, or EIA-96 letter-number codes, printed directly on the component body. This tool is designed for through-hole color-band resistors. For SMD codes, the 3-digit system works as: first two digits are significant figures, third digit is the power-of-ten multiplier (e.g., 472 = 47 × 100 = 4,700 Ω = 4.7 kΩ).