Construction Monkey

Wire Properties


The Construction Monkey Conductor calculator lets you figure out electrical characteristics of wires including the ampacity, circular mills, area, resistance, reactance, impendance, conduit fill, and voltage drop.

Make your selections below and the form will automatically update the values.


Circular Mills
Outside Diameter

Conduit Properties

Voltage Drop

Max Voltage Drop Max Length
2% Voltage Drop
3% Voltage Drop
5% Voltage Drop
Good design practices limit wire ampacity due to over current to 80% of rated ampacity under most circumstances.
The wire size will not be able to handle this load and it will cause catastrophic failures.
Good design requirements should limit overall voltage drop to less than 5%.


  1. Ampacity based NEC 2017 Table 310-16, which is based on three (3) current carrying conductors at 30 degrees Celsius Ambient.
  2. Calculations based on 0.85 Power Factor.
  3. Based on NEC2017 Table 9.
  4. Check Conductor De-Rating Factors for more than three (3) current carrying conductors.
  5. Load for Voltage Drop is calculated based on 80% ampacity load of maximum allowable ampacity.

No guarantees are made as to the accuracy of the calculation or compliance with local codes.  Verify all calculations with a professional engineer. If you find an error, or have a suggestion, please send us an email.