Can I import an existing model from Revit, AutoCAD or SAP2000?

DXF import (from AutoCAD) is supported: you can import a 2D skeleton of your structure and CalcSteel will create the bar network with nodes and members. For Revit, the recommended workflow is to export a simplified DXF or IFC from Revit first. Native IFC import is planned. Direct import from SAP2000, ETABS or Robot is not supported because their file formats are proprietary and complex. For migration from these tools, the fastest path is usually: reconstruct the geometry from a DXF or screenshots. Most small-to-medium steel frames can be re-modeled in CalcSteel in under 30 minutes using templates (warehouse, portal frame, truss) as starting points.