DWG to DGN converter: how to convert DWG to MicroStation DGN

The DWG to DGN converter most people already have is AutoCAD's DGNEXPORT command, and the most faithful one is MicroStation itself, which opens DWG and saves DGN. This viewer does not write DGN or DWG (it displays DWG and DXF files only), so this page explains seed files, mapping setups, batch conversion, and what to check, so the DGN lands correctly in a Bentley project.

What changes between DWG and DGN

DGN is Bentley's native format for MicroStation, used heavily by transportation departments and utilities. It organizes a drawing differently from DWG: layers become levels, blocks become cells, xrefs become references, linetypes become line styles, and model space becomes a design model. DGN V8 also works in "master units" and "sub units" (for example meters and millimeters) with a fixed resolution, which is why unit mapping is the single most common source of errors.

A seed file is the DGN template the conversion starts from. It defines units, the working area, 2D or 3D, and the default settings. Agencies that require DGN deliverables normally supply their own seed file, and using it is not optional: the same DWG exported with a metric seed and an imperial seed ends up at different sizes in MicroStation.

Which DWG to DGN converter for which case

How to convert DWG to DGN in AutoCAD with DGNEXPORT

1. Clean the DWG first: PURGE unused blocks and layers, AUDIT, and bind or detach xrefs, because each xref becomes a DGN reference that must travel with the file.
2. Type DGNEXPORT, choose V8 DGN (V7 only if the recipient still uses it), and enter a file name.
3. In the Export DGN Settings dialog, pick the seed file: the one your client supplied, or an AutoCAD default seed (imperial or metric, 2D or 3D) from the AutoCAD support folder.
4. Set the conversion units: tell AutoCAD whether one DWG unit equals a master unit or a sub unit in the seed. A DWG in millimeters with a seed of meters/millimeters maps to sub units.
5. Choose how to handle references: "Translate all DWG references to DGN files" creates matching DGN references; "Bind" merges them in.
6. Open Mapping Setups and create a setup that maps DWG layers to DGN levels, DWG linetypes to DGN line styles, lineweights, and colors. Save it for reuse; it also runs from a script with -DGNEXPORT.
7. Click OK. Open the result in MicroStation or Bentley View to verify, as described below.

AutoCAD LT does not include DGNEXPORT. Also note DGNIMPORT exists for the reverse trip, covered on DGN to DWG.

MicroStation, batch conversion, and ODA-based tools

MicroStation opens DWG files natively and uses a DWG work mode. The conversion is a save: File > Open the DWG with the correct seed file selected under Options, check that the drawing sits at the right size, then File > Save As and choose MicroStation V8 DGN. Settings under File > Settings > DWG/DXF Open control unit mapping, level names, and text style handling, and because Bentley maintains these settings, the output is usually closer to what a MicroStation user expects than AutoCAD's export.

For folders, use Utilities > Batch Converter in MicroStation: add the DWG files, set the output format to V8 DGN and the seed file, and run. This is the standard way agencies convert deliverables in bulk.

The Open Design Alliance's SDK reads and writes DGN as well as DWG, and several commercial converters are built on it. The free ODA File Converter, however, converts only between DWG and DXF versions, so it does not produce DGN on its own. Bentley View, which is free, opens DWG and DGN for viewing, measuring, and printing, which makes it the right tool for checking a converted file if you lack MicroStation.

What to check in the DGN

• Units and size. Measure a known distance in MicroStation or Bentley View. A factor of 1000 or 25.4 means the master/sub unit mapping was wrong.
• Levels. Layer names should appear as level names; a single "Default" level means the mapping setup was skipped.
• Line styles and weights. Custom AutoCAD linetypes without a mapped style come through as solid lines.
• Text and fonts. SHX and TrueType fonts map to MicroStation fonts; check special characters and text heights.
• References. Each former xref must be present as a DGN file next to the main file.
• Cells. Blocks become shared cells; attributes become tags or plain text depending on the setting.

Before converting, it helps to know exactly what the DWG contains. Open it on dwgviewer.app to list the layers and count entities, with nothing uploaded; the page DWG layers explains what to look for. If the recipient can accept DXF instead, DXF to DGN follows the same settings.

Frequently asked questions