Online Calculators and Tables to Help You Determine Proper Wire Size


The Wire Ampacity Calculator will quickly calculate the maximum allowable current through a conductor based on wire size (AWG or kcmil), wire insulation, conductor type and installation method.

Wire Ampacity Calculator


Enter the information below to calculate the maximum allowable ampacity for current-carrying conductors.






Maximum Ampacity: 25 Amps

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 Ampacity 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 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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