DGN to DWG Converter

What is DGN to DWG Conversion?

Converting DGN to DWG transforms an engineering drawing from the native format of the Bentley CAD program into the working format of the mainstream Autodesk CAD system. The contents of the source file (lines, arcs, complex chains, B-splines, multilines, closed shapes, cells, hatches, dimensions, text elements, references to external files) are transferred into DWG with geometry, coordinates, colors, and user attributes preserved. The result is a drawing that opens in an AutoCAD-compatible environment as a regular working document: it can be edited with familiar tools, supplemented with custom blocks, organized into layouts, equipped with viewports, prepared for plotting, and stored in the common project structure alongside other DWG files.

DGN is the binary CAD format from Bentley, native to a specialized CAD program oriented toward infrastructure design. It is used to design highways and railways, bridges, tunnels, metro systems, airports, hydraulic structures, oil and gas facilities, master plans for large territories, and land surveying materials. The file stores the drawing together with levels (Levels), elements of various geometry, cells (analogous to blocks), hatches, dimensions, text, reference files (References), custom coordinate systems, and often a tie to geographic coordinates. There are two main branches of the format: the legacy V7 and the modern V8/V8i, which differ in internal structure and feature sets. A unique feature of DGN is that a single file can contain several independent models (Models), each with its own geometry and coordinate system.

DWG is the proprietary working format of the mainstream Autodesk CAD system and has become the de facto industry standard. In DWG, the drawing structure is optimized for daily work: along with geometry, the file stores layers, blocks (including dynamic blocks), dimension styles, text styles, external references (Xref), layouts, viewports, plot settings, custom object properties, and saved views. DWG is the primary format for most architectural, structural, and engineering firms worldwide: it carries packages for architectural, structural, mechanical, plumbing, electrical, and HVAC disciplines, exchanges files between subconsultants, and accumulates libraries of standard details and title-block templates.

Converting DGN to DWG is a transition from the Bentley ecosystem to the Autodesk ecosystem. After conversion, the infrastructure drawing becomes accessible for work in any AutoCAD-compatible environment: it can be opened, edited, supplemented, merged with architectural and structural sections of the package, and handed to a subcontractor that does not hold a Bentley license. Conversion is especially common when an infrastructure project was developed in the specialized Bentley CAD program but further work on the package, inclusion in a larger project, or delivery to a building contractor takes place in the mainstream CAD system.

Comparing DGN and DWG

The main difference is belonging to two different CAD ecosystems. DGN remains the working tool of the infrastructure designer in which the object is created, tied to the terrain, and brought to a deliverable version inside the specialized Bentley CAD program. DWG is the working format of the mainstream Autodesk CAD system, used by the vast majority of architectural, structural, and engineering firms. When an infrastructure object must be embedded in a common project, handed to subconsultants, delivered to a building contractor, or continued in an AutoCAD-compatible environment, DGN to DWG conversion becomes unavoidable. After the conversion, the drawing becomes an equal part of the package in the mainstream industry format and does not require the recipient to install Bentley software.

When to Use DWG Instead of DGN

Handing an infrastructure project to a subcontractor on the mainstream CAD system

Infrastructure objects (a stretch of road, an interchange, a bridge crossing, a tunnel portal, a rail station yard) are typically designed in the specialized Bentley CAD program because it has discipline-specific add-ons for alignment, longitudinal profile, and cross sections. But for downstream disciplines (landscaping, small architectural forms, fencing, pavilions, lighting poles, noise barriers), subcontractor firms are usually engaged, and they work in the mainstream CAD system. Handing them the source as DGN is difficult: small architectural firms and engineering shops rarely hold Bentley licenses. Converting DGN to DWG turns the infrastructure source into a format the subcontractor opens in the familiar environment, overlays their own disciplines on top, and returns the result into the common package.

Continuing work on the project in an AutoCAD-compatible environment

Within a single organization, teams may work in the specialized Bentley CAD program on some projects and in the mainstream CAD system on others. When the infrastructure source has arrived from a neighboring department or a subconsultant, and all further work on the discipline runs in the Autodesk environment (because corporate layer standards, dimension styles, and block libraries are configured there), it is convenient to convert the incoming DGN to DWG right away. After that, the drawing falls into the familiar working environment: it opens with the configured template, picks up corporate styles, and is referenced via Xref from neighboring DWG files.

Delivering drawings to a building contractor

Building contractors and subcontractors rarely keep Bentley licenses: production is oriented toward the mainstream CAD system because most architectural and structural drawings arrive in it. To deliver a working package of the infrastructure scope to the construction site (alignment drawings, track plans, road striping schemes, interchanges, small infrastructure objects), source DGN files are converted to DWG. After that, superintendents, foremen, and crew leaders on site work with the familiar format: they open the file on a field laptop, print it on the contractor's standard plotter, and cross-check it with the architectural and structural scope in a single environment.

Bridging Bentley and Autodesk CAD standards

Large complex projects are often split between contractors: one part is delivered in Bentley (infrastructure, hydraulics, oil and gas), another in Autodesk (architecture, structures, building systems). To consolidate disciplines into a single project document flow, infrastructure DGN files are converted to DWG, after which the package is maintained in one CAD environment. This eliminates the need to keep both licenses at every workstation and simplifies project support across all stages, from development through construction administration.

Combining infrastructure with architecture in a unified package

When a transport interchange, an infrastructure site, an interchange with adjacent buildings, or a bridge crossing with pavilions and approaches is being designed, infrastructure designers (working in the specialized Bentley CAD program) and architects with structural engineers (working in the mainstream CAD system) act in parallel. To obtain a final consolidated plan in one environment, infrastructure sources are converted to DWG. Then the architects overlay their drawings via external references, the structural team docks in foundation sections, and the systems engineers place utilities, all in a single format and a single CAD system.

Integrating with other project disciplines

Architectural sections, structural sections, HVAC, plumbing, electrical lighting and power, automation and communications - in the overwhelming majority of cases these are produced in the mainstream CAD system. When the infrastructure scope from DGN must be added to this package, the source is converted to DWG and loaded as an external reference or pasted into a common sheet. After that, all disciplines fall into a single working pipeline without additional transitions between CAD programs.

Sending to fabrication shops and production lines

Fabrication shops (steel structures, sheet-metal parts, road signs, posts, fences) are oriented toward the mainstream CAD system: technologists and operators are used to working with DWG, and shop drawings and bills of materials are produced in it. To order the manufacture of infrastructure elements for a project executed in the specialized Bentley CAD program, the sources are converted to DWG. The shop receives the familiar format, cuts sheet metal, bends profiles, cuts pipes, and assembles parts for subsequent delivery to the site.

Collaborating with subcontractors that do not hold a Bentley license

Most architectural, structural, engineering, and estimating organizations do not purchase Bentley licenses: that product line is targeted at large infrastructure operators. To start collaborative work with such partners, the infrastructure client publishes part of the sources in DWG. This removes the software barrier for partners and lets each of them work in the familiar CAD system, returning results back through DWG.

Technical Aspects of Conversion

Mapping Levels to Layers

Levels are the backbone of DGN drawing organization. Each level has a numeric identifier, name, color, line type, weight, and visibility state. Layers in DWG are conceptually similar: name, color, line type, weight, and state (on, frozen, locked). During conversion, each DGN level is transferred to the corresponding DWG layer with names, colors, and basic parameters preserved. If the source file used numeric identifiers without meaningful names (some infrastructure projects are organized this way), after opening in the AutoCAD-compatible environment it is worth renaming the layers according to the organization's adopted standard so that the package aligns with the rest of the project disciplines.

Converting cells (Cells) into blocks

Cells in DGN are reusable groups of elements, conceptually close to blocks in the mainstream CAD system. During conversion, each cell gets its own block definition in DWG, and its placements turn into regular block inserts with coordinates, rotation, and scale. Complex cells with nested elements are transferred in full: nested blocks are also created in the block table. If the cell relied on parametric capabilities of Bentley-specific constructs, after conversion they turn into static geometry: dynamics and parametrics analogous to dynamic blocks of the mainstream CAD system do not appear automatically. When needed, they are added as separate work after opening the drawing.

Multilines and complex chains

Multilines and Complex Chains are typical DGN elements actively used in infrastructure design: they describe shoulders, curbs, medians, and layered pavement structures. DWG has its own multiline analog, but the syntax and set of settings differ: offset widths, joint handling, end caps. Simple parallel lines are transferred correctly, while complex multilines are sometimes simplified into a set of separate polylines with geometry preserved. After opening the drawing in the mainstream CAD system, check multilines visually and, if necessary, rebuild them using styles adopted in your organization.

Fonts and text elements

Fonts are one of the most problematic spots when crossing between CAD ecosystems. Bentley uses its own SHX fonts and custom font sets that are not present in the mainstream CAD system by default. When the required font is missing, the program substitutes a default font and the visual appearance of annotations changes slightly: line widths, line breaks, and overall look. The text itself remains readable, but title blocks and labels may look a bit different from the source. To minimize discrepancies, agree on the font set with the infrastructure contractor in advance, or replace rare fonts in the text styles of the resulting DWG with the standard SHX and TrueType fonts adopted by your organization.

Scale and units of measurement

Infrastructure drawings are often produced in meters with geographic coordinates, while architectural and structural drawings - in millimeters in a local coordinate system of the construction site. During conversion, the units and coordinates of the source DGN are transferred as is, and after opening in the mainstream CAD system the drawing may appear at an unexpected scale for the user. Check the unit parameters in the resulting DWG and, if necessary, rescale the drawing to the units adopted for the project so that insertion via external reference or copy-paste into another DWG works correctly. This is especially important when an infrastructure fragment is to be combined with the architectural and structural scope.

Geo-referencing and coordinate systems

DGN often carries a geographic reference: the drawing has real coordinates in a regional coordinate system, a project survey grid, or a global geodetic system. DWG also supports geo-referencing, but the implementation differs. During conversion, coordinates are transferred and the drawing keeps its position in space. If the recipient plans to use the infrastructure fragment as a geo-referenced underlay below the architectural and structural package, after opening it in the mainstream CAD system check the geo-coordinates and, if necessary, define the coordinate system parameters with the tools of your CAD program. This is especially important for topographic bases, master plans, and site layouts.

Handling multi-model DGNs

A single DGN file can contain several independent models (Models): a drafting model with the main geometry, separate models for different levels of detail, sheet models with print layouts, and auxiliary models. DWG is organized differently: a single file has one Model Space and a set of layouts (Paper Space). During conversion, each DGN model either becomes a separate DWG document or is merged according to an agreed rule: the main model becomes the Model Space of the output DWG, DGN sheets are transferred to Paper Space, and auxiliary models remain as separate files. This is convenient because a set of several DWG files is easier to share with subconsultants and store in a common project directory.

Custom line styles and hatches

Bentley supports a rich system of custom line styles: with variable width, with embedded cells, with lengths in real-world units. The DWG analog is line types, which can also carry symbols and labels, but the implementation and parameter sets differ. During conversion, standard line types are transferred correctly, while complex custom styles are sometimes simplified to basic geometry or replaced with the nearest equivalent. Hatches are also transferred: DGN patterns are rewritten into DWG hatch types, and most standard patterns appear recognizably. After opening the drawing, check hatches visually, especially in complex pavement structures, and replace them with project-standard ones if needed.

Which Files Are Best Suited for Conversion

Ideal candidates:

• Infrastructure object plans and schematics (roads, interchanges, sites, landscaping schemes) that need to be passed to an architectural or structural subconsultant
• Topographic bases and master plans from the infrastructure department for use as an underlay in the mainstream CAD system
• Drawings of small architectural forms, fences, noise barriers for delivery to fabrication shops
• Interchange and node schematics for coordination with the architectural and structural part of the complex
• Archive DGNs that require edits and rework in the Autodesk environment
• Alignment and corridor drawings produced by the infrastructure department for combination with the architecture of a station or terminal building

Suitable, but with caveats:

• Drawings with a large number of multilines and complex chains - check the result visually and rebuild the elements if needed
• Files with reference files (References) - make sure all dependent DGN files and rasters are delivered alongside the main file
• Drawings in geographic coordinates tied to terrain - verify the coordinate system in the resulting DWG
• Multi-model DGNs with several Models - decide in advance how to distribute the models across output DWG files
• Drawings with custom line styles and hatches - complex custom sets may be simplified, check visually
• Files with text in rare Bentley fonts - agree the font set or replace styles with standard ones after opening

Not worth converting:

• DGNs where work continues in the specialized Bentley CAD program and there are no plans to hand off to subconsultants
• Narrowly specialized infrastructure models that rely on Bentley domain add-ons and that, when reproduced in DWG, turn into static geometry and lose the connection with the add-on
• Files where all work is built on parametric links specific to Bentley add-ons

Advantages of the DWG Format

DWG offers several key advantages over DGN for most participants in the design process.

Mass industry adoption. The AutoCAD-compatible environment is installed in the vast majority of architectural, structural, and engineering organizations. Delivering a file in DWG requires nothing from the recipient beyond an ordinary CAD program and removes the question of compatibility with expensive specialized licenses.

A ready-made ecosystem of project disciplines. Architecture, structures, HVAC, plumbing, power, and automation - in the mainstream CAD system these are traditionally produced in DWG. When the infrastructure source is converted to DWG, it embeds into the common disciplinary package as an equal participant without the need for conversion at every step.

Compatibility with building contractors. Superintendents, foremen, technologists, and operators on the construction site and in fabrication shops in most cases work with the mainstream CAD system. DWG opens at their workstations directly and enters the production flow without intermediaries.

External reference (Xref) support. The DWG external reference mechanism makes it possible to load an infrastructure fragment as an underlay into an architectural or structural drawing and to automatically reflect its updates. This substantially simplifies collaborative work of large teams on a complex project.

Compatibility with organizational templates and standards. DWG templates, dimension styles, block libraries, color schemes, and corporate layer standards apply to a converted infrastructure drawing as a matter of course. After opening the DWG in the mainstream CAD system, it is easy to bring the drawing to the corporate look.

Support across a wide range of AutoCAD-compatible environments. Beyond the classic mainstream CAD program, DWG is read and written by numerous alternative CAD programs and viewers. This gives every project participant freedom to choose tools without dependence on a single license.

Familiarity for architects, structural engineers, and systems engineers. Most specialists from adjacent disciplines in a design firm are used to working in DWG. Delivering the infrastructure source in this format does not require learning a new CAD program and does not create a barrier to collaboration.

Convenience for archiving in the common project directory. When the entire project documentation set is stored in DWG, the infrastructure portion in the same format enters the archive naturally. All files open the same way, are searched the same way, and are versioned the same way.

Limitations and Recommendations

The main limitation is the difference in CAD ecosystem concepts. Bentley and Autodesk developed their products independently, so DGN has capabilities with no direct DWG analog, and vice versa. Complex cells, custom line styles, and Bentley-specific parametric links turn into static geometry in the mainstream CAD system. After conversion, check such elements visually and, if necessary, rebuild them with the tools of the AutoCAD-compatible environment.

The second limitation is multilines and complex chains. These DGN elements are actively used in infrastructure design, but their DWG analog is organized differently. Simple parallel lines are transferred correctly, while complex constructs are sometimes simplified into a set of separate polylines. Inspect multilines visually, especially in pavement drawings and complex infrastructure constructs.

The third limitation is fonts. Bentley uses its own SHX sets and custom fonts that are not present in the mainstream CAD system by default. In their absence, the program substitutes a default font, and the visual appearance of annotations changes slightly. Agree on the font set with the infrastructure contractor in advance, or replace rare fonts in the styles of the resulting DWG with standard ones.

The fourth limitation is geo-referencing. Infrastructure drawings are often produced in geographic coordinates, while architectural and structural ones - in a local coordinate system of the site. After conversion, check the coordinates and, if necessary, set the coordinate system parameters with the tools of your CAD program. This is especially important for topographic bases and master plans that will be placed below other disciplines.

The fifth limitation is multi-model DGNs. A single source file may contain several models, and during conversion they are either distributed across several DWG files or merged according to an agreed rule. Agree with the contractor in advance on how the models should be split so that you receive the expected DWG set.

After conversion, open the resulting DWG in the mainstream CAD system, walk through the layer manager, check the block structure, visually inspect the drawing across its main fragments, and, if needed, bring layers to corporate names, replace styles with those adopted in the organization, and reconfigure title blocks. This will turn the infrastructure source into a full-fledged part of the working drawing package.