What is a DWG file and when do you need one?
If an architect, designer or builder asks you to send your drawings as a DWG file, they want a drawing they can keep working on in their own software. A DWG file is AutoCAD’s file format: the drawing is stored as editable objects in layers at real-world dimensions, rather than as a flat image. If all you have is a PDF or a paper drawing, that is not necessarily a problem — but it is worth checking exactly what kind of file you have first. This guide explains what a DWG is, when you really need one, how to open it without AutoCAD, how to quickly check which kind of PDF you have, and what to ask the person requesting it before you order.
What is a DWG file?
DWG is AutoCAD’s native file format. It has been part of AutoCAD since the very first version in 1982, and today many other CAD programs use it too.
In a DWG file the drawing is stored as editable objects at real-world size — the lines, blocks and dimensions that make up walls, doors and measurements. In a well-made file the objects are organised into layers — walls, furniture, dimensions and text kept separate, for example — so the designer can switch a layer off, move a wall or draw their own design on top of the existing plan. That is why people ask for a DWG: it is a working file, not a picture.
Sometimes you will be asked for a DXF instead of a DWG. DXF is an exchange format created by Autodesk that many programs can open even if they do not support DWG.
When do you need a DWG?
You usually need a DWG when the drawing is going to be changed or used as the basis for another project. If you only need to view, print or archive the drawing, a legible PDF is enough. Three situations come up again and again in the enquiries we receive:
Renovation or alterations. The designer wants to start from a plan of the existing building, not from a blank sheet.
Building services. Whoever designs the heating, plumbing, ventilation or electrical installation needs an architectural background drawing to draw their systems on. One such client asked us for a plan specifically without the old pipework, so that the new design could be drawn on a clean background.
Property management and letting. A management company wants a plan of its rental units that it can update itself every time the layout changes.
How is a DWG different from a PDF?
A PDF is meant for viewing and printing: it preserves the appearance of the sheet, but you cannot edit it the way you edit a CAD working file. Broadly speaking, PDFs of drawings fall into two categories, and the difference determines how much work is needed to create a DWG.
A PDF saved from CAD software. The lines and text are still in the file as lines and text. Since the 2017 release, AutoCAD can import the lines and text of such a PDF as its own objects. That is a good start, but the layers, scale and text usually need to be checked and tidied up.
A scanned PDF. This is a picture of a paper drawing: the software sees no lines, only pixels. AutoCAD does not turn an image into lines — to get a DWG, the drawing has to be redrawn.
A drawing of an older house, flat or office building that came from an archive or turned up in a drawer is usually the second kind.
How can you tell which kind of PDF you have?
The quickest check is to open the PDF and zoom in closely on the drawing:
the lines and letters stay sharp — the PDF was probably saved from CAD software;
the lines go blurry and the background is grey or yellowish — it is probably a scanned image.
Same living room, same zoom: on the left, a scanned PDF in which the floor area figure can no longer be read reliably; on the right, our AutoCAD plan.
The look of the sheet helps too: folds, stamps, yellowed paper and handwritten notes suggest that you are looking at a scan of a paper original.
How do you open a DWG file without AutoCAD?
You do not need to buy AutoCAD just to look at a drawing. Autodesk offers free viewers: DWG TrueView is a Windows program that opens DWG and DXF files, and Autodesk Viewer runs in the browser. With them you can view and measure a drawing; to edit it, you need CAD software.
If a DWG will not open, one possible reason is the version. The DWG format has several generations: AutoCAD releases 2018–2027 all save in the 2018 format, and an older AutoCAD version cannot open a file saved in a newer DWG format. Ask the sender to save the file in an older format, or convert it yourself with DWG TrueView.
What should you ask before ordering?
Three questions save both time and money:
Which sheets are needed? An old drawing set may contain dozens of sheets, but the designer often needs only one or two floor plans. In one enquiry, we were sent 11 drawings from two partly overlapping drawing sets, so we asked the client to confirm which of them were actually needed before we quoted.
Is redrawing the existing drawing enough? A DWG made from an old drawing shows what is on the old drawing, not the building as it is today. If the house has been altered since, mark the changes on the drawing or add the measurements.
Which format and layer structure are needed? Ask whether a DXF will also do, which DWG version is needed and whether there is an in-house layer standard — we can follow it if required.
Example: an old plan with the client’s changes marked on it
A private client in Iceland sent us two scanned sheets: the old floor plan of the house and the same sheet with the planned changes marked on it by hand — walls to be removed, new rooms, and door and window sizes.
We redrew the plan in AutoCAD with the changes included: walls, doors and windows, dimensions, and room names and floor areas in Icelandic. If any part of the original is illegible, we mark it visibly on the drawing rather than guessing.
Frequently asked questions
Can I convert a PDF to DWG myself? If the PDF was saved from CAD software, AutoCAD can import its lines and text as its own objects, but the result usually needs tidying up. With a scanned PDF this does not work: the drawing has to be redrawn.
How can I open a DWG file for free? With Autodesk’s free viewers: DWG TrueView (Windows) and Autodesk Viewer, which runs in the browser. To edit the drawing, you need CAD software.
Can a DWG be made from a photo or a hand sketch? Yes, we also work from phone photos and hand sketches. How accurate the drawing is depends on how clear the material is and how many measurements are provided.
How do you get a DWG if you only have a PDF or paper?
The simplest route is to ask for the original: if the drawing was made on a computer at some point, the DWG may still be held by the original designer or developer that produced it. If you have no drawing at all, our guide to finding the old plans of your flat or house can help.
If there is no editable original, a new DWG has to be made. We do this by hand in AutoCAD: you send the PDF, scanned file or photo, we assess the scope and send you a free quote with a delivery time. Before we send the final files, you can review a watermarked draft; the result is an editable DWG and a PDF. We usually complete a single drawing or a couple of simpler sheets within 3 working days. If the drawing is on paper, scan it rather than photographing it with your phone: a photo taken at an angle introduces perspective distortion, and dimensions may be difficult to read in a small image. The whole process is described in our guide to digitising old drawings.
A redrawn DWG is a base drawing, not a building design — it does not replace the work of the architect or engineer responsible for the design.
Need the same for your drawing? We can do it for you: Floor plan and drawing digitization — send us your drawing and get a free quote.
Comments