Select 4-band resistor colors to calculate resistance (Ω) and tolerance in real-time, or find color bands for a given resistance value.
Resistors limit current flow in electronic circuits and use color bands to indicate resistance values. 4-band resistors are the most common type: the first and second bands represent digits, the third band is the multiplier (power of 10), and the fourth band is tolerance. For example, [Brown-Black-Red-Gold] = 1kΩ ±5%. Calculation: Brown(1), Black(0) = 10, Red(×100) = 10 × 100 = 1,000Ω = 1kΩ, Gold = ±5%.
Color code table: Black(0), Brown(1), Red(2), Orange(3), Yellow(4), Green(5), Blue(6), Violet(7), Grey(8), White(9). Multipliers: Black(×1), Brown(×10), Red(×100), Orange(×1k), Yellow(×10k), Green(×100k), Blue(×1M), Violet(×10M), Gold(×0.1), Silver(×0.01). Example: [Yellow-Violet-Red-Gold] = 47 × 100 = 4.7kΩ ±5%.
Tolerance indicates resistance accuracy. Gold = ±5%, Silver = ±10%, No band = ±20%. A 1kΩ ±5% resistor has actual resistance between 950Ω ~ 1,050Ω. Precision circuits require ≤5% tolerance, while 10% is sufficient for general circuits.
Example 1: [Brown-Black-Red-Gold] = 1(Brown) 0(Black) × 100(Red) = 1kΩ ±5%. Example 2: [Red-Red-Orange-Gold] = 2(Red) 2(Red) × 1k(Orange) = 22kΩ ±5%. Example 3: [Yellow-Violet-Yellow-Gold] = 4(Yellow) 7(Violet) × 10k(Yellow) = 470kΩ ±5%.
E12 series (±10% tolerance): 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 multiplied by powers of 10. E24 series (±5%): includes double the values of E12.
LED current limiting resistor: R = (Supply Voltage - LED Voltage) / LED Current. Example: 5V supply with red LED (2V, 20mA): R = (5-2) / 0.02 = 150Ω. Use nearest standard value 180Ω. Power calculation: P = I² × R. For 20mA, 150Ω: P = (0.02)² × 150 = 0.06W. Use 1/4W (0.25W) resistor.