Construction Monkey

Electrical Calculation Home

Improve Estimates With Productivity Data From the Field

Construction Monkey Calculators

Are you in need of electrical calculations done quickly based on current electrical engineering practices and the National Electrical Code? Construction Monkey has compiled several programs to assist in electrical construction, design and engineering. We are constantly adding new calculations and improving the existing calculations. All calculations are free to use, but please read the Terms of Use for more specific information.


Calculates ampacity or power or voltage of a circuit. It also calculates the wire size for the circuit calculated.

Calculates the wire and conduit size for various feeders and circuits.  It also calculates the voltage drop and allows you to limit the voltage drop so the feeder size will be increased.

Calculates the power, ampacity, feeder, and overcurrent protection on a specific motor size and voltage. It also calculates the voltage drop of the circuit you specified for the feeder portion.

Calculates the feeders and overcurrent protection for different types of transformers. It also calculates the voltage drop on the primary and secondary sides of the transformer.


Tables of various conduit properties including interior and exterior diameters for various types of electrical conduit.

Tables of various wire/conduit properties including fill quantities for various sizes and types of conduit and wire.

The Construction Monkey Conduit Selector will provide you with the appropriate conduit size based on the number of conductors that you have to install.

Calculates the duct bank size based on the quantity of conduits, the size and type of conduit. The calculator let's you know the amount of dirt to remove, the amount of dirt to return, the amount of concrete for a duct bank, and the amount of left over dirt.


Gives all the applicable information for different types of conductors in different conduits.

Gives all the applicable information for different types of conductors in different conduits.

Tables of various wire properties including ampacity, diameter for various insulation types, and impedance and resistance values.


Calculates the minimum cubic volume required for a device or junction boxes based on NEC 313.16.

Calculates the service size for a single residential unit utilizing the NEC optional method.


Calculate the manpower requirements for a project given the start and end dates, the hours, and the revenue. Based on accurate historical norms, this can project each weeks manloading requirements as well as peak worker requirements. It also provides earned revenue projections per month.

Need to know what will happen when productivity changes on a project. This easy to use calculator provides you with the information you need to know what changes in productivity will do to enhance your project.

Need to calculate the total hours of your install? This easy calculator will provide you with the information of total hours and a lot more information.

Improve Estimates With Productivity Data From the Field

Combining the data across multiple projects, you can understand trends and update your estimating database to reflect actual productivity measures or to ensure your next project has enough hours to be successful.

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.