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🎨 Resistor Color Code Calculator

Determine the resistance value, tolerance, and temperature coefficient of any resistor by selecting its color bands. Supports both 4-band standard resistors and 5-band precision resistors.

Band 1 (1st digit)

Band 2 (2nd digit)

Band 3 (multiplier)

Band 4 (tolerance)

What is this tool?

A resistor color code is a universal marking system used on through-hole resistors to indicate their resistance value, tolerance, and sometimes temperature coefficient. Instead of printing numbers on a tiny component, manufacturers paint colored bands around the cylindrical body. Each color corresponds to a digit (0–9), a multiplier (power of ten), or a tolerance percentage. The system was standardized decades ago and remains ubiquitous in electronics education, prototyping, and repair work. This calculator supports the standard 4-band system, which is the most common type found in hobby electronics, Arduino kits, and through-hole PCB assemblies. The first two bands represent the first two significant digits of the resistance value. The third band is the multiplier, which tells you how many zeros to add (or where to place the decimal point). The fourth band indicates the tolerance — how much the actual resistance may deviate from the stated value. For example, a resistor with brown, black, red, and gold bands has a value of 1 kΩ with a ±5% tolerance, meaning the actual resistance is somewhere between 950 Ω and 1,050 Ω. Whether you are an electronics student learning to read color codes, a maker building your first Arduino project, or an engineer troubleshooting a circuit board, this tool saves you the mental gymnastics of memorizing the color chart and eliminates the risk of misreading a band under poor lighting.

How it works

The resistor color code system assigns each color a specific numerical meaning. The table below shows the complete standard mapping:

Color	Digit	Multiplier	Tolerance
Black	0	×1	—
Brown	1	×10	±1%
Red	2	×100	±2%
Orange	3	×1K	—
Yellow	4	×10K	—
Green	5	×100K	±0.5%
Blue	6	×1M	±0.25%
Violet	7	—	±0.1%
Gray	8	—	—
White	9	—	—
Gold	—	×0.1	±5%
Silver	—	×0.01	±10%

To read a 4-band resistor, hold it so the tolerance band (usually gold or silver, spaced farther from the others) is on the right. The calculator takes the first two digits, multiplies them by the third band value, and applies the tolerance band to compute the range. For instance, bands of yellow (4), violet (7), orange (×1K), and gold (±5%) give 47,000 Ω ±5%, which is a common 47 kΩ resistor.

How to use

Select the color of the first band (first significant digit).
Select the color of the second band (second significant digit).
Select the color of the third band (multiplier).
Select the color of the fourth band (tolerance).
Click Calculate to see the resistance value and tolerance range.

Frequently Asked Questions

How do I know which side of the resistor to read from?

The tolerance band (usually gold or silver) is spaced farther apart from the other three bands. Hold the resistor so this gap is on your right, then read from left to right. If there is no gap, look for the gold or silver band — it is always the tolerance band.

What is the difference between 4-band and 5-band resistors?

A 4-band resistor uses two significant digits, a multiplier, and a tolerance band. A 5-band resistor adds a third significant digit, allowing for tighter tolerances (like ±1% or ±0.1%) and more precise values. This calculator currently supports the 4-band system, which covers the vast majority of hobbyist and educational resistors.

Why is my measured resistance different from the color code value?

The color code gives the nominal value, but the actual resistance falls within the tolerance range. A 100 Ω resistor with ±5% tolerance can measure anywhere from 95 Ω to 105 Ω and still be within spec. Also, measuring with fingers touching the probes adds body resistance, and cheap meters have their own internal error. Use high-quality probes and avoid touching the metal tips.

Can I use this for surface-mount (SMD) resistors?

No, SMD resistors use a different marking system with numbers, not color bands. A 3-digit code like "472" means 47 × 10² = 4,700 Ω, and a 4-digit code like "4701" means 470 × 10¹ = 4,700 Ω. This calculator is only for through-hole resistors with painted color bands.

What does the temperature coefficient band mean?

On 6-band resistors, the sixth band indicates the temperature coefficient in ppm/°C (parts per million per degree Celsius). It tells you how much the resistance changes with temperature. Brown (100 ppm/°C) is common for general precision resistors, while orange (15 ppm/°C) is used for ultra-stable applications.

What are the most common resistor values I will encounter?

In Arduino and hobby electronics kits, you will frequently see 220 Ω, 330 Ω, 1 kΩ, 4.7 kΩ, 10 kΩ, and 100 kΩ resistors. These correspond to common E12 and E24 series values. Learning to recognize these by sight speeds up your prototyping significantly.

Tips & Advice

Always read resistor color bands from the side closest to the band group — the tolerance band is typically spaced farther apart. If you are unsure of the direction, look for the gold or silver band (tolerance) and place it on the right. Under poor lighting, brown and red can look similar; use a bright light or a magnifying glass. For surface-mount resistors (SMD), color codes do not apply — they use numeric markings instead (e.g., 472 = 47 × 10² = 4.7 kΩ). When working with vintage or military-spec resistors, you may encounter an additional fifth band for temperature coefficient (brown = 100 ppm/°C, red = 50 ppm/°C). Always double-check your reading with a multimeter if precision matters.

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