The National Electrical Code Handbook, publication NFPA 70, is the source of the NEC Allowable Ampacities of Insulated Conductors table. The table may be downloaded from NECConnect.org in document form. Many electrical wire manufacturers and electrical suppliers publish extracts or reproductions of the NEC chart on their web sites.
The NEC wire gauge ampacity chart is table 310.15(B)(16) in the 2014 NEC Handbook published by the National Fire Protection Association. The ampacity recommendations in the table have been adopted in all U.S. states as wiring safety standards. The table provides the maximum electrical current, in units of amperes, that a conductor can safely carry continuously as determined by its material type, temperature rating and diameter.