Quickly determine resistor values and tolerances from color bands with accuracy. Perfect for electronics projects, circuit design, and educational purposes
Precision rating
Lower bound
Upper bound
Resistors are passive electronic components that limit the flow of electric current in a circuit. They are fundamental building blocks in electronics, used to control voltage levels, limit current, and divide voltages. The resistance value determines how much the resistor opposes the flow of current, measured in Ohms (Ω).
Key Point: Resistors follow Ohm's Law: V = I × R, where V is voltage, I is current, and R is resistance. This fundamental relationship is crucial for circuit calculations.
In electronic circuits, resistors serve multiple purposes including current limiting, voltage division, biasing active components, and providing feedback in amplifier circuits. Understanding resistor values is essential for anyone working with electronics, from hobbyists building simple circuits to engineers designing complex systems.
The resistor color code system was developed in the 1920s to provide a standardized method for indicating resistance values. Instead of printing numbers on the small resistor body, colored bands are used to represent digits and multipliers. This system is internationally standardized and used worldwide.
| Color | Digit Value | Multiplier | Tolerance | Temp Coeff |
|---|---|---|---|---|
| Black | 0 | ×1 | - | 250 ppm/°C |
| Brown | 1 | ×10 | ±1% | 100 ppm/°C |
| Red | 2 | ×100 | ±2% | 50 ppm/°C |
| Orange | 3 | ×1K | - | 15 ppm/°C |
| Yellow | 4 | ×10K | - | 25 ppm/°C |
| Green | 5 | ×100K | ±0.5% | 20 ppm/°C |
| Blue | 6 | ×1M | ±0.25% | 10 ppm/°C |
| Violet | 7 | ×10M | ±0.1% | 5 ppm/°C |
| Gray | 8 | ×100M | ±0.05% | 1 ppm/°C |
| White | 9 | ×1G | - | - |
|
|
- | ×0.1 | ±5% | - |
| Silver | - | ×0.01 | ±10% | - |
Pro Tip: Use our percentage calculator to quickly compute tolerance ranges for your resistor values.
Reading resistor color codes follows a systematic approach. The bands are read from left to right, starting from the band closest to one end of the resistor. The key is identifying which end to start from.
Example: Brown-Black-Red-Gold
= 1kΩ ±5%
Example: Brown-Black-Black-Red-Brown
= 10kΩ ±1%
Example: Red-Red-Black-Brown-Brown-Red
= 2.2kΩ ±1% 50ppm/°C
Tolerance indicates how much the actual resistance value can vary from the nominal (marked) value. It's expressed as a percentage and is crucial for circuit design accuracy. Lower tolerance values indicate higher precision resistors.
1kΩ ±5% Resistor
Actual value: 950Ω to 1050Ω
Range: ±50Ω
1kΩ ±1% Resistor
Actual value: 990Ω to 1010Ω
Range: ±10Ω
Circuit Design Tip: Use our percentage calculator to determine if resistor tolerances will affect your circuit's performance.
Different types of resistors are used for various applications. Understanding the characteristics of each type helps in selecting the right component for your project.
Power rating indicates the maximum power a resistor can dissipate without damage. Exceeding this rating can cause the resistor to overheat, change value, or fail completely.
Power dissipated by a resistor can be calculated using:
P = V² / R or P = I² × R or P = V × I
Where P = Power (Watts), V = Voltage (Volts), I = Current (Amps), R = Resistance (Ohms)
Safety Rule: Always use a resistor with a power rating at least 2x higher than the calculated power dissipation to ensure reliable operation and prevent overheating.
Temperature coefficient (TC) indicates how much a resistor's value changes with temperature. It's measured in parts per million per degree Celsius (ppm/°C). This is especially important in precision circuits and extreme temperature environments.
Example: 10kΩ resistor, 100 ppm/°C
Temperature change: +50°C
Resistance change: +50Ω (0.5%)
New value: 10.05kΩ
Use our percentage calculator to compute temperature-induced changes.
Resistors serve many functions in electronic circuits. Understanding these applications helps in selecting appropriate values and types for your projects.
Protect LEDs and other components from excessive current.
Formula: R = (Vsupply - VLED) / ILED
Example: 5V supply, 2V LED, 20mA → R = 150Ω
Create reference voltages and sensor interfaces.
Formula: Vout = Vin × (R2 / (R1 + R2))
Use equal values for 50% division
Define logic states in digital circuits.
Typical values: 1kΩ to 10kΩ
Lower values = stronger pull, higher current
Set operating points for transistors and op-amps.
Application: Amplifier design
Critical for proper amplifier operation
Design Tip: For complex calculations involving multiple resistors, use our scientific calculator to handle the math efficiently.
Resistors are manufactured in standard values based on the E-series system. This ensures consistent availability and helps with circuit design standardization.
Multiply by 1, 10, 100, 1K, 10K, 100K, 1M, etc.
More values available for precise designs
Low Values (Ω)
Mid Values (kΩ)
High Values (kΩ)
Very High (MΩ)
Knowing how to test and troubleshoot resistors is essential for circuit debugging and component verification.
Multimeter Testing
In-Circuit Testing
Overheating
Mechanical Damage
Selection Guidelines
Installation Tips
Classic Mnemonic
"Big Boys Race Our Young Girls But Violet Generally Wins"
Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White
Alternative Version
"Bad Beer Rots Our Young Guts But Vodka Goes Well"
Same color sequence, different phrase
Use Apps
Camera-based color detection
Magnifying Glass
For small components
Multimeter
Always verify measurements
High-precision resistors with tolerances as low as ±0.01% are used in measurement equipment and reference circuits.
Special resistors designed for extreme temperature environments up to 300°C or higher.
Power resistors for high-current applications, motor drives, and power supplies.
Resistors designed for RF and microwave applications with minimal parasitic effects.