Prior to 2024, AutoCAD LT did not support AutoLISP. For newer LT versions, LISP is supported. If TLEN fails, consider the AutoCAD Add-ins Store TotalLength.

Lee Mac Programming offers a similar advanced "Total Length & Area" program if you require more complex features. Steps to Download and Save: Copy the code from the GitHub link above. Open Notepad on your computer. Paste the code.

A reliable script is available on GitHub - tlen.lsp .

Modern versions of AutoCAD feature strict security controls to prevent malicious scripts from running. If your file path isn't trusted, AutoCAD will block the LISP.

The humble tlen.lsp is a testament to the power and flexibility of AutoLISP. For years, it has provided a quick and free solution for summing lengths in AutoCAD. While the original script can sometimes falter in modern versions, the path to making it work is well-understood. By following the loading and troubleshooting steps in this guide, you can keep this classic tool in your workflow.