WinCalcMCP

WinCalcMCP is an MCP server that lets Claude Desktop offload calculations to Windows Calculator via PowerShell. It receives math expressions from Claude, sanitizes them, executes them using PowerShell's math capabilities, and returns precise results back to Claude. This creates a seamless experience where Claude can request arithmetic, percentages, roots, and other supported functions and receive accurate outputs powered by Windows native tooling. The server runs in the background and integrates automatically with Claude Desktop so you don’t need to manually start or stop it each time.

To use it, configure Claude Desktop to point at the MCP server by adding an MCP entry in claude_desktop_config.json with the path to server.js. Once configured, Claude can ask questions like “What is 123 × 456?”, “Calculate 15% of 2,847”, or “Solve: (25 + 17) × 3 - 8,” and the server will handle the calculation and return the result. The server supports basic arithmetic, parentheses, decimal numbers, and math functions provided by PowerShell, ensuring accurate results by delegating computation to Windows’ native engine.

Prerequisites:

• Windows Operating System
• Node.js (version 16.0.0 or higher)
• Claude Desktop (Windows version)
• PowerShell (built into Windows)

Installation steps:

1. Clone the repository git clone https://github.com/rspeciale0519/WinCalcMCP.git cd WinCalcMCP

2. Install dependencies npm install

3. Test the server (optional) node server.js You should see: Windows Calculator MCP server running... Press Ctrl+C to stop.

4. Configure Claude Desktop to use the MCP server (see configuration instructions in the README).

• The MCP server runs as a background process managed by Claude Desktop after initial configuration.
• Ensure your claude_desktop_config.json points to the correct server.js path, e.g., "args": ["C:\path\to\your\WinCalcMCP\server.js"].
• If you encounter permission issues running PowerShell, you may need to adjust PowerShell execution policy: Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
• This server relies on Windows PowerShell for calculations; ensure PowerShell is available and accessible from the environment where the MCP server runs.
• For troubleshooting, verify Node.js is installed, the path in Claude Desktop config is correct, and Claude Desktop is restarted after changes.