How to Read Resistor Color Codes, Step by Step

Most small through-hole resistors are too tiny to print numbers on, so they use colored bands instead. Once you learn the system, you can read any resistor in a few seconds. This guide walks you through it step by step.

The color values

Each color stands for a digit. Memorise this list; it is the heart of the whole system.

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

Many people use a mnemonic to remember the order. Any sentence where the first letters follow B, B, R, O, Y, G, B, V, G, W works; invent one that sticks for you.

Step 1: Find the first band

Hold the resistor so the bands are on the left. The tolerance band (often gold or silver) is usually set slightly apart from the others and sits on the right. Start reading from the opposite end. If you cannot tell which end is which, look for the band group that is closer to one edge: that edge is the start.

Step 2: Count the bands

Most resistors have four or five bands.

• 4-band: digit, digit, multiplier, tolerance.
• 5-band: digit, digit, digit, multiplier, tolerance (used for higher-precision parts).

Step 3: Read the digits

Write down the digits for the first two bands (or three for a 5-band). Place them side by side, not added together. Brown then black gives 10, not 1.

Step 4: Apply the multiplier

The next band tells you how many zeros to add, i.e. a power of ten. Using the same digits as the colors above: black ×1, brown ×10, red ×100, orange ×1,000, yellow ×10,000, green ×100,000, blue ×1,000,000. Two special multipliers exist: gold ×0.1 and silver ×0.01.

Step 5: Read the tolerance

Tolerance shows how far the real resistance may differ from the marked value. Common bands are:

• Brown = ±1%
• Red = ±2%
• Gold = ±5%
• Silver = ±10%

A 1,000 Ω resistor with ±5% tolerance could legitimately measure anywhere from 950 Ω to 1,050 Ω.

Worked examples

Example 1: 4-band (brown, black, red, gold)

1. Brown = 1, black = 0, so the digits are 10.
2. Red multiplier = ×100, so 10 × 100 = 1,000 Ω.
3. Gold = ±5%.

The result is 1 kΩ, ±5%.

Example 2: 4-band (yellow, violet, orange, gold)

1. Yellow = 4, violet = 7, so the digits are 47.
2. Orange multiplier = ×1,000, so 47,000 Ω.
3. Gold = ±5%.

The result is 47 kΩ, ±5%.

Example 3: 5-band (red, red, black, brown, brown)

1. Red, red, black = 2, 2, 0, so the digits are 220.
2. Brown multiplier = ×10, so 2,200 Ω.
3. Brown tolerance = ±1%.

The result is 2.2 kΩ, ±1%.

Example 4: using gold as a multiplier (brown, black, gold, gold)

The digits are 10 and the multiplier is ×0.1, giving 1 Ω, with ±5% tolerance.

Writing values the usual way

Electronics uses prefixes to keep numbers short: 1,000 Ω is 1 kΩ, and 1,000,000 Ω is 1 MΩ. You will often see them shortened further in schematics, such as 4k7 meaning 4.7 kΩ. Practise converting back and forth.

Double-check with a multimeter

Colors can be hard to tell apart, especially brown versus red, orange versus red, or blue versus violet under poor light. When in doubt, measure. Set a digital multimeter to its resistance (Ω) range, touch the probes to each lead and read the display. Remove the resistor from the circuit first, otherwise other parts can give a false reading, and avoid pinching both leads with your fingers, as your body adds its own resistance. If you need a meter, look at the selection of test equipment and multimeters. The measured value should land within the tolerance range of the marked one.

Why the value matters

A classic use is the series resistor for an LED. Using Ohm's law, resistance equals the voltage you need to drop divided by the current you want. If a 5 V supply drives an LED with a forward voltage of about 2 V at 10 mA, the resistor must drop the remaining 3 V, so R = 3 ÷ 0.01 = 300 Ω. You would choose a nearby standard value, such as 330 Ω. Always check the LED's datasheet for its actual figures. For parts to practise with, see the available resistors, and pair them with some LEDs.

Tips and pitfalls

• Use good light. Daylight or a white lamp helps tell similar colors apart.
• Beware faded bands. Old or heat-damaged resistors can discolor. Measure them.
• Standard values. Resistors come in preferred series (such as E12 and E24), so you will rarely find, say, 1,234 Ω. If your calculation gives an odd number, pick the nearest standard value.
• Power rating. Color bands do not show wattage. Small resistors are commonly rated around a quarter watt, but check the packaging, and use a higher rating when a circuit dissipates more heat.
• Surface-mount parts use printed numbers instead of colors. A code of 472 means 47 followed by two zeros, so 4,700 Ω.

Keep a printed chart near your workbench for the first few weeks. Before long you will decode bands without looking, and your breadboard projects will go much faster.