Online Calculators and Tables to Help You Determine Proper Wire Size


The Wire Size Calculator below will calculate the proper wire size for a circuit based on circuit amps, preferred (or available) wire insulation, conductor type and installation specifications. For more advanced considerations, use the Wire Size Calculator or the Advanced Wire Size Calculator.

Quick Wire Size Calculator


Enter the information below to calculate the appropriate wire size.







Appropriate Wire Size: -

Note: These values are based on allowable ampacities of insulated conductors rated up to and including 2000 volts, not more than three current-carrying conductors in a raceway, cable, or Earth, single-insulated conductor in free air, and an ambient air temperature of 30°C (86°F).

Source: NFPA 70, National Electrical Code Table 310.15(B)(16-17)

For ambient temperatures other than 78°F - 86°F, or more than three current-carrying conductors in a raceway, cable or Earth, use the Advanced Wire Size Calculator. This takes into account correction factors for voltage drop, temperature and the number of current-carrying conductors.


For long conductor runs where voltage drop may be an issue, use the Voltage Drop Calculator to determine voltage drop and the Circuit Distance Calculator to determine maximum circuit length. Visit the Tables page to view reference tables such as Maximum Ampacity for Current-Carrying Conductors.


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