Mike Holts Electrical Toolbox is a free iPhone app developed by Mike Holt Enterprises Inc. for electricians, inspectors, instructors, contractors, and engineers. It is a comprehensive app that contains a wealth of information related to electrical work.

The app includes conductor sizing, circuit protection sizing, race sizing, and equipment grounding conductor sizing for electric heating equipment, air-conditioning equipment, motors, transformers, and dwelling-unit service calculations and sizing. It also provides information on voltage drop limitations for conductor sizing.

Overall, Mike Holts Electrical Toolbox is a practical and useful app for anyone working in the electrical industry. The app is user-friendly and easy to navigate, providing comprehensive information for a range of electrical work scenarios.