Netcalc is a practical command-line tool designed for practicing IPv4 and CIDR subnet calculations. It is part of LayerByte's educational cybersecurity projects, prioritizing a practical and readable approach for defensive learning. The tool's development focused on creating a single-concept project for easier code comprehension and testing. Netcalc is intended for school purposes only and emphasizes safety and responsible use. Its defensive scope includes accepting only local or authorized input and providing beginner-readable output. The project features clear validation and error handling. It explicitly avoids any malicious activities like credential theft, brute forcing, exploitation, malware, evasion, or destructive behavior. Useful learning activities involve reading the code, testing with authorized samples, and comparing input with output. Netcalc is built using C++ and is licensed under MIT. Feedback is welcomed to keep the project safe, clean, and useful for educational purposes.