Junction box sizing is based on the National Electrical Code (NEC) requirements. A 25% safety factor is added to ensure adequate. A fiber optic junction box, also known as a fiber optic distribution box or termination box, is a protective enclosure that facilitates the connection and management of fiber optic cables. It serves as a central point for organizing and distributing optical fibers, ensuring efficient connectivity. This document provides information on sizing junction boxes and determining conductor bending radii according to NEC standards. Our simple spreadsheet configurator will help to guide you with regards to calculating your containment sizing requirements. Reel count is ceil (Total ÷ ReelSize), and the rounded order length equals Reels × ReelSize. Choose your unit and keep it consistent.