Resistor Calculator – Guide & Formulas
Decode 4-band resistor color codes to identify resistance values (Ohms) and tolerances.
Decode electronics hardware. Select band colors for your standard 4-band axial resistor to calculate nominal resistance, tolerance bounds, and typical visual band arrangements.
Key Takeaway
Use the free Resistor Calculator to decode 4-band resistor color codes to identify resistance values (ohms) and tolerances. Get instant results with step-by-step explanations.
How to Use the Resistor Calculator
- Select the color of Band 1 (representing the first significant digit).
- Select the color of Band 2 (representing the second significant digit).
- Select the color of Band 3 (representing the multiplier exponent).
- Select the color of Band 4 (representing the manufacturer tolerance margin).
- Review output resistance in ohms, kilo-ohms, or mega-ohms alongside color bands.
The Formula
Variable Definitions
- d1 / d2: The first and second physical color bands denoting numeric values
- 10^M: The third band exponent multiplying overall scale factor
- T: Tolerance margin percentage of actual resistance
Decoding a Yellow-Violet-Red-Gold Resistor
Calculate resistance values for a resistor labeled with Yellow (4), Violet (7), Red (x100), and Gold (±5%) bands.
- Step 1: Identify numeric digits: Yellow = 4, Violet = 7. Combine digits: 47.
- Step 2: Apply multiplier: Red = 10^2 = 100. Multiply: 47 × 100 = 4,700 ohms.
- Step 3: Factor tolerance: Gold = ±5%.
- Step 4: Final specification: 4.7 kΩ with a guaranteed tolerance margin of ±5%.
Frequently Asked Questions
What does a high tolerance percentage mean?
High tolerance (e.g., ±10% Silver) indicates the actual physical resistance can fluctuate further from the nominal printed value. High-precision applications use ±1% or ±0.5% resistors.
How do I read a five-band resistor?
Five-band resistors add a third significant digit band before the multiplier, providing high accuracy for precision hardware.