Resistor Calculator
Calculate resistor values from color codes, find color codes for resistance values, and determine power ratings for electronic circuits and projects.
Resistor Color Code
Standard Resistor Values
Common Resistor Values
Results
Visual Resistor
🔧 Common Applications:
- • LED current limiting
- • Base resistors
- • Voltage dividers
How to Read Resistor Color Codes
To read resistor color codes:
- Identify the number of color bands (4, 5, or 6)
- Orient the resistor with the tolerance band (usually gold or silver) on the right
- Read the bands from left to right
- For 4-band resistors: 1st digit, 2nd digit, multiplier, tolerance
- For 5-band resistors: 1st digit, 2nd digit, 3rd digit, multiplier, tolerance
- For 6-band resistors: add temperature coefficient as the 6th band
- Calculate: (digits) × (multiplier) ± (tolerance)%
Resistor Color Code Chart
| 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 | ×10M | ±0.1% |
| Gray | 8 | ×100M | ±0.05% |
| White | 9 | ×1G | - |
| Gold | - | ×0.1 | ±5% |
| Silver | - | ×0.01 | ±10% |
Example: 4-Band Resistor
Color Bands: Red, Violet, Brown, Gold
Calculation:
- 1st Band (Red): 2
- 2nd Band (Violet): 7
- 3rd Band (Brown): ×10
- 4th Band (Gold): ±5%
Result: 27 × 10 = 270Ω ±5%
Value Range: 256.5Ω to 283.5Ω
Frequently Asked Questions
What does the tolerance band indicate?
The tolerance band shows the accuracy of the resistor value. Gold = ±5%, Silver = ±10%, Brown = ±1%, Red = ±2%. A smaller tolerance percentage means higher precision.
How do I determine which end to start reading from?
The tolerance band (usually gold or silver) is typically placed closer to one end. Start reading from the opposite end. If unsure, try both directions and see which gives a standard resistor value.
What is the difference between 4-band and 5-band resistors?
5-band resistors have an additional digit band, providing more precise values. 4-band resistors typically have ±5% or ±10% tolerance, while 5-band resistors often have ±1% or ±2% tolerance.