Fix AutoCAD DWG Scale in ArchiMaster 3D (2026)

When an AutoCAD DWG or DXF lands in ArchiMaster 3D home design software at the wrong size, the fix is not to redraw the plan. Measure one known dimension on the imported underlay, compute the scale factor, rescale the underlay in the properties panel, and only then trace the walls at true size. In most cases the correction takes under five minutes. The usual cause is a unit mismatch between millimeters, centimeters, meters, inches, or feet, often introduced during export or when a drawing was drawn in one system and imported into another. The process below works for full floor plans, site surveys, and kitchen and bath drawings.

• A wrong-scale DWG import is almost always a unit mismatch, not a corrupt file. Check millimeters, centimeters, meters, inches, and feet before redrawing anything.
• Measure one known wall or door opening on the underlay first. A 900 mm wall, a 36 inch door, or a 3 foot module gives you the ratio you need.
• The scale factor is the true dimension divided by the measured dimension. For example, a door that measures 60 inches in the file but should be 36 inches uses a factor of 0.6.
• Rescale the imported underlay before tracing. Tracing at the wrong scale, then scaling walls later, doubles the work and invites dimensional errors.
• After rescaling, verify a second known dimension. Correct scale is confirmed only when two unrelated elements measure correctly.

Why Your DWG Imports at the Wrong Scale

AutoCAD drawings are often unitless internally. One drawing unit can mean a millimeter, an inch, a meter, or a foot depending on the template, and the file's insertion scale is not always exported correctly. When ArchiMaster 3D imports a DWG or DXF, it has to assign a real-world unit to each drawing unit. If the file was drawn in millimeters but the importer reads meters, the plan arrives 1000 times too large. If it was drawn in inches but read as feet, it arrives 12 times too small. The same mismatch can happen when a surveyor sends a metric site plan and you work in an imperial project. This is a scale problem, not a damaged file, and it is corrected with one scale factor.

Measure a Known Dimension Before You Rescale

Start with a dimension you trust: a door leaf, a window opening, a stair tread, a bathtub, or a labeled dimension on the drawing. Use the dimension tool in ArchiMaster 3D to measure between two exact snap points, not rough picks. Write down the measured length in the current project units. Then compute the scale factor as true dimension divided by measured dimension. If you cannot find a good reference, use a code-known element. A standard interior door is 32 or 36 inches wide (813 or 914 mm); a standard bathtub is 60 inches (1524 mm); a typical stair tread is 11 inches (279 mm); a standard garage door opening is 9 or 16 feet (2743 or 4877 mm). Avoid using an overall exterior dimension unless it is clearly labeled, because wall thickness and overhangs vary.

• Interior door: 32 or 36 in (813 or 914 mm)
• Bathtub: 60 in (1524 mm)
• Stair tread: 11 in (279 mm)
• Standard garage door opening: 9 or 16 ft (2743 or 4877 mm)
• Kitchen counter depth: 25.5 in (648 mm), including the countertop overhang

Scale Factor Formula

The scale factor is always true dimension divided by measured dimension. Write it as a decimal, not a percentage. If the plan is too small, the factor is greater than 1. If the plan is too large, the factor is less than 1. This one number corrects the entire underlay. For example, a wall segment that should be 10 feet but measures 120 inches uses a factor of 120 divided by 120, or 1.0, only if the units are already consistent. A bath vanity that should be 60 inches but measures 1524 millimeters needs a unit conversion first. Enter the factor once, then verify a second element before tracing.

Rescale the Imported Underlay in ArchiMaster 3D

Select the imported underlay with the select tool, then open the Properties panel. Find the scale field and enter the factor you calculated. Suppose a door opening should be 36 inches, but the dimension tool reads 60 inches. The factor is 36 divided by 60, or 0.6. Enter 0.6 and apply. If the file was drawn in millimeters but imported as meters, the plan can arrive 1000 times too large, so the factor is 0.001. If it was imported 12 times too small, use 12. The same factor applies to the whole underlay because imported geometry scales uniformly. Do not rescale walls after tracing. Scaling wall objects after they have been placed can change wall thickness and door casing positions. Correct the underlay first.

“You do not fix a scaled drawing by tracing at the wrong size. You fix the underlay, then trace once.”, ArchiMaster 3D scale correction workflow

Align and Rotate the Underlay to the Grid

After scaling, the plan may still be rotated or offset from the project origin. Use the move and rotate tools on the underlay, not on individual wall segments. In ArchiMaster 3D, select the underlay, choose the rotate tool, click a base point at a known corner, and enter the rotation angle needed to bring a long exterior wall parallel to the X axis. Then use the move tool to place a known corner at 0,0 or at a meaningful grid intersection. Aligning the underlay before tracing makes wall snaps cleaner and reduces tiny angle errors that compound across a long plan. Avoid dragging with the mouse for final positioning; type the exact angle and distance.

Trace Walls at True Size, Not Over the Underlay

With the underlay correctly scaled and aligned, trace the walls using ArchiMaster 3D's wall tool. Snap to the real endpoints and type the actual wall thickness, such as 5.5 inches for a 2x6 framed wall or 140 mm for a standard metric stud. Use ArchiMaster 3D's wall and room tools to place walls, doors, and windows at their true sizes. Do not adjust wall thickness to visually match the underlay if the underlay was exported with line weights inflated. The wall tool records true dimensions, so a 12 foot wall remains 12 feet regardless of the imported line style. Keep the DWG underlay on its own layer so you can toggle it off and check the traced model for gaps, overlaps, and clean corners.

Prevent Future Scaling Errors with Correct Units

The fastest way to avoid the rescale step is to agree on drawing units before the file leaves AutoCAD. In AutoCAD, run the -DWGUNITS command to check what the file assumes; in ArchiMaster 3D, set the project units to match before importing. If a surveyor sends a metric site plan, open a metric project. If the architect works in inches, keep the project imperial. When you receive a DXF, ask whether one drawing unit equals a meter or a millimeter. A one-sentence clarification prevents a 1000x error. For repetitive work, save a template with the correct units, grid, and layer set so every new project starts consistent. You can test a mixed-unit workflow with the free trial from the ArchiMaster 3D downloads page.