Online Calculators and Tables to Help You Determine Proper Wire Size
The Resistor Color Code Calculator will calculate the resistance value in Ohms (Ω) for 4-band and 5-band resistors based on the color code on the resistor.
4-Band Resistor Color Code Calculator
Choose resistor color code to calculate resistance value.
Resistance values can be calculated from a 4-band resistor color code as follows:
- Band 1: First significant figure (left-most digit)
- Band 2: Second significant figure
- Band 3: Multiplier (determines order of magnitude)
- Band 4: Tolerance value (%)
For example, a resistor with a color band pattern of red, green, yellow, gold yields the first digit as 2, the second digit as 5, and a multiplier of 10,000. This produces a resistance value of with a ± 5% tolerance.
5-Band Resistor Color Code Calculator
Choose resistor color code to calculate resistance value.
Resistance values can be calculated from a 5-band resistor color code as follows:
- Band 1: First significant figure (left-most digit)
- Band 2: Second significant figure
- Band 3: Third significant figure (additional digit of precision)
- Band 4: Multiplier (determines order of magnitude)
- Band 5: Tolerance value (%)
For example, a resistor with a color band pattern of brown, red, orange, red, gold yields the first digit as 1, the second digit as 2, the third digit as 3, and a multiplier of 10,000. This produces a resistance value of with a ± 5% tolerance.
To calculate wire size for a circuit, use the Wire Size Calculator or the Advanced Wire Size Calculator. To calculate wire ampacity for a circuit, use the Wire Ampacity Calculator or the Advanced Wire Ampacity Calculator.
For long conductor runs where voltage drop may be an issue, use the Voltage Drop Calculator to determine proper conductor sizing and maximum circuit length. Visit the Tables page to view reference tables such as Maximum Ampacity for Current-Carrying Conductors.
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