The Engineering ToolBox and Maryland Metrics are two organizations that have charts showing pipe thread sizes on their websites. Common American national standard pipe taper threads are the NPT and NPTF, says The Engineering ToolBox.
The Engineering ToolBox provides additional information about threads, including the difference between male and female thread types, and warns that the sizes listed in its chart do not necessarily correspond to a pipe's physical dimensions. Maryland Metrics provides a range of charts for different countries.
The primary difference between the NPT and NPTF standards is that NPTF pipe threads typically require no sealant or Teflon tape, notes The Engineering ToolBox. Pipes with NPTF-standard threads do not need sealant because the threads are adjusted such that they physically inhibit leakage, reports Wikipedia.